Replacing outlet; 3 pairs of wires in box, 2 are hot

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  #1  
Old 07-31-12, 06:26 AM
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Replacing outlet; 3 pairs of wires in box, 2 are hot

I'm replacing some old outlets in one of the bedrooms in our house. The house was built in the late 60's/early 70's, and as far as I know it's the original outlets that I'm replacing. Most of the outlets have 2 pairs of wires and are a relatively easy replacement job. One of the outlets has 3 pairs of wires coming in to it though. They are all pushed into the back of the outlet (8 holes in the back of this outlet). I've tested each pair with a multimeter. Two of the black wires are hot, the third one isn't. I'm wondering how to hook up the new outlet, which just has 4 screws. The box is already very crowded with wires, so introducing any jumper wires is going to be very difficult. Also, with the non-hot pair disconnected, every other outlet in the room still works - so it apparently isn't a feed line for the other outlets.
 
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  #2  
Old 07-31-12, 06:50 AM
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How were the wires connected to the old receptacle?

Was the tab between the top and bottom of the old receptacle broken?
 
  #3  
Old 07-31-12, 07:34 AM
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The tab is not broken on the old outlet.

When viewing the outlet from the rear, here is the layout of the holes and wires:

1 2 3 4

5 6 7 8

1=Black B
2=empty
3=White B
4=empty
5=Black C
6=Black A
7=White A
8=White C

Black A is the one that isn't hot.
 
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Old 07-31-12, 08:14 AM
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What is the voltage measuring between the two blacks that measure hot? Is there a switch? Are you sure there is no red wire?
 
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Old 07-31-12, 08:17 AM
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You mean connect the multimeter directly to the two black hot wires? All I've tested so far is black to white.

There's a switch in the room, but it doesn't appear to be relevant here. The voltage readings I've taken are the same with the switch off or on.
 
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Old 07-31-12, 08:42 AM
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I've tested each pair with a multimeter. Two of the black wires are hot, the third one isn't.
Something appears to have been incorrectly wired at some point outside the box where this receptacle is.

Did you remove all of the wires from the old receptacle before testing?

Are the two hot feeds on the same circuit?

Is either one of them controlled by a switch?

Do you see anything that goes on and off as you connect and disconnect the wires in Cable A?
 
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Old 07-31-12, 08:54 AM
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When I connect the multimeter leads to the two hot black wires, the multimeter reads 0. When I connect it to a hot black and its matching white wire, they read ~114.

So far I have only removed the wire pair A - the non-hot one. B and C are still connected to the old outlet via the back-stab method.

The two hot feeds are on the same circuit. Not sure about the dead feed. Every other circuit in the house is on, with the exception of the dedicated (presumably) circuit for our well pump. That is off because our well is currently broken.

The light switch in the room controls the ceiling fan/light, and both the fan and light are operational with wire pair A disconnected.

A couple of months ago I went through and mapped out every electrical item in our house to figure out what was on each circuit. The circuit box was very poorly labeled. This circuit controls the outlets and ceiling light for two upstairs bedrooms, the light and most of the outlets in the upstairs bathroom, and one set of kitchen lights downstairs. With wire pair A disconnected from the outlet in question, every other item on this circuit is functional.

Hmm, one other oddity I just remembered. In the upstairs bathroom, there's a triple wall switch. When we moved in to the house, the top switch controlled the bathroom wall light, the middle switch controlled the ceiling exhaust fan, and the bottom switch occasionally worked to turn on the light built into the ceiling fan.

Well, at some point we lost power to both of the bedrooms on this circuit. (This was when I decided to map out the circuits, when I was troubleshooting this problem.) I ended up replacing the switch in the bathroom, and got the wall light and exhaust fan working again. Before replacing the bathroom switch, the old bottom switch would sometimes trip the circuit. We just don't use the bottom switch on the new switch. Not sure if any of that is relevant to the current outlet question, but it is part of the same circuit so figured I'd better mention it.
 
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Old 07-31-12, 09:49 AM
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I just realized that no one has talked about hot-to-neutral vs. hot-to ground in this thread, or I missed it. Is there a difference in the reading if you touch the second probe to ground rather than neutral?

So far I have only removed the wire pair A - the non-hot one. B and C are still connected to the old outlet via the back-stab method.
Label each cable. With the power off, remove and separate all of the wires. With the power back on, test each pair for voltage.

Only one pair should read hot. If that is what you find, You should splice the blacks, the whites and the grounds together, by color, with a pigtail added to each, and attach the pigtails to the new receptacle. If you need more space, you can replace the box with a deeper old-work box.

If you still find that both cables B and C read hot, post back and we can help you resolve that.
 

Last edited by Nashkat1; 07-31-12 at 10:23 AM.
  #9  
Old 07-31-12, 09:54 AM
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I just realized that no one has talked about hot-to-neutral vs. hot-to ground in this thread, or I missed it. Is there a difference in the reading if you touch the second probe to ground rather than neutral?
I haven't tried that. I'll try that later this afternoon when I can get to it again.

Are you saying that the likely reason both connected black wires are hot is because they're both connected to the outlet? i.e. one is actually dead, but it's reading hot because it's getting power from the other one via the outlet?
 
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Old 07-31-12, 10:19 AM
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Are you saying that the likely reason both connected black wires are hot is because they're both connected to the outlet?
Yes. Voltage readings need to be taken with the wires disconnected except for reasons that don't apply here.
 
  #11  
Old 07-31-12, 06:19 PM
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Ok, I disconnected all the wires and found that C is the one that is hot. Also discovered that with all wires disconnected from this outlet, the other bedroom on this circuit has no power. The bathroom does, however.

So, presumably B is the feed to the other bedroom then, since the other bedroom still had power with just A disconnected. Still not sure what the purpose of A is.

Does this information change the directions at all?

If not, how do I change to a deeper box? I'm guessing that requires cutting out some of the plaster board, something I'd really like to avoid if at all possible as I just did an entire new paint job in this room.
 
  #12  
Old 07-31-12, 06:52 PM
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Attach a pigtail* to all the blacks. Attach a pigtail* to all the whites. Attach the pigtails to the receptacle. Unless it is an unusually shallow box you should have room. Grounds are also pigtailed to the receptacle and if the box is metal to the box.

*A pigtail is a short wire ~6 inches long the same size and color as the wires it is attached to.

Note if you want to change a box there is no reason to cut any sheet rock out. Just slip a hack saw blade between the stud and the box and cut the nails holding it. Wrap duct tape around one end of the hack saw blade to make a handle. A Sawzall will also do the trick. You would then insert an old work box. The hole may actually have to be enlarged slightly for an old work box.

The ears you see are flat when inserted then raised behind the Sheetrock to hold the box in place after insertion.
 
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Old 07-31-12, 08:47 PM
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Still not sure what the purpose of A is.
Nor are we, since you aren't sure.

Given that, your choices are to include it in the splice and hope that the other end is either connected to a load or device, or safely dead-ended in another box or to leave it out, cap off the wires, and hope that there isn't anything connected to it that will require you to reopen this box and connect it later.

Given the scenarios, plus the fact that having it connected hasn't caused any problem, I think I'd go with the first option.
 
  #14  
Old 08-01-12, 06:53 AM
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Alright, thank you both for the info. I'll try to add the pigtails using the existing box. Theoretically I think there's room. This is fairly heavy duty wire - doesn't bend easily (I'm not familiar with specific wire sizes or I'd give you the exact size), so I'm just wondering if I'll be able to get everything squeezed in there given the relative inflexibility of the wires involved. I'll find out later tonight when I attempt it!
 
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Old 08-01-12, 07:03 AM
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Fold the wire accordion style before inserting into the box._/\/\/\_
Assuming #12 you need 22.5 cubic inches to be code compliant. You can measure the box to determine if your code compliant or look for a number stamped into it.

Older "gangable" metal boxes may have only 12.5 inches and should be replaced with a deep old work box.
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  #16  
Old 08-01-12, 03:10 PM
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It's an old metal box. Just over 12 cubic inches if my quick measurements were correct. I'm heading to the store tonight to pick up the parts I'll need for this.
 
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Old 08-01-12, 03:17 PM
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Just a note before you venture out. Most old work boxes are plastic. They can't be used with metallic (AKA BX) cable.
 
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Old 08-01-12, 04:46 PM
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I'm not familiar with types of cable. If by metallic you mean the exterior sheathing around each cable, I don't believe these are metallic, but I'll peer in the corners of the box more closely to see for sure before I start.

If I get the old box out but don't have time to get the new box in and everything hooked up at the same time, can I temporarily tie all of the blacks and whites together with wire nuts for overnight and leave it like that and then finish the job tomorrow?

The new (old work) box was labeled 20 cubic inches. That was the highest they had. There was another one made out of more rigid plastic that was only 18 cubic inches.
 
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Old 08-01-12, 05:18 PM
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can I temporarily tie all of the blacks and whites together with wire nuts for overnight and leave it like that and then finish the job tomorrow?
Yes. In fact that is a good test to see if we have given you the correct instructions.

If by metallic you mean the exterior sheathing around each cable, I don't believe these are metallic
Good. You will be able to see for sure when you pull the box out.

The new (old work) box was labeled 20 cubic inches. That was the highest they had.
Is the breaker 15 amp or 20 amp?
 
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Old 08-01-12, 05:30 PM
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Is the breaker 15 amp or 20 amp?
15 amp.

The exterior sheathing is not metal.
 
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Old 08-01-12, 06:28 PM
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15 amp.

The exterior sheathing is not metal.
It sounds like your cables are Type NM, AKA Romex. Also, on a 15A circuit, the wires should be 14AWG, which means that you need 20% less room in the box for the wires. It's puzzling, though, that you said that
This is fairly heavy duty wire - doesn't bend easily
Hm. At any rate, the box fill calculation is 1 conductor volume for each conductor entering the box, plus 1 for all the EGCs (the ground wires) put together, plus 2 for the receptacle. That's a total of 9.

With 14AWG wire, each wire-related unit requires 2 in.[SUP]3[/SUP], so that works out to 18 in.[SUP]3[/SUP] needed. With 12AWG wire, each wire-related unit requires 2.25 in.[SUP]3[/SUP]. Since the receptacle stays at 2, that works out to 19.75 in.[SUP]3[/SUP].

The new (old work) box was labeled 20 cubic inches
So, either way, you should be OK with that box, assuming it doesn't have any internal cable clamps.
 

Last edited by pcboss; 08-03-12 at 11:07 AM.
  #22  
Old 08-01-12, 06:32 PM
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I'm pretty sure it's 12-2 wire. For that reason, I was expecting to find a 20amp circuit when I went downstairs to check, but it says 15. I bought 12-2 wire at the store tonight, so I'll find out for sure when I compare the new wire to the old.
 
  #23  
Old 08-01-12, 07:04 PM
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Ugh. I'm going to have to expand the hole a fair amount to even get to the nails holding the existing box in. There's a tab at the top - and presumably bottom as well - with a nail through the tab into the stud. It appears that the tabs are offset somewhat from the box too, not sure how that's possible, but that's what it looks like from the small hole I have opened up to see inside the wall. I hope I can get the hole expanded enough evenly without expanding it too much - I'm a bit worried about that as it is plaster.
 
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Old 08-01-12, 07:06 PM
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Good. We are almost there. When you pull the old box you should be able to see the size on the cable sheath.
 
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Old 08-01-12, 07:19 PM
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I'm going to have to wait and resume this tomorrow because the kids need power in the other bedroom now. I'll post an update tomorrow once I get the old box out.

Thanks for all of your help ray2047 and Nashkat1.
 
  #26  
Old 08-01-12, 08:13 PM
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I just discovered that one of the outlets in the other bedroom on this circuit no longer works. Wondering now if wire pair A is a feed to that outlet. It'd be kind of odd, since the outlets still work on either side of the non-functioning outlet. I'll hook A back up tomorrow first and see if that outlet starts working again.
 
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Old 08-01-12, 08:36 PM
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I'm going to have to expand the hole a fair amount to even get to the nails holding the existing box in. There's a tab at the top - and presumably bottom as well - with a nail through the tab into the stud. It appears that the tabs are offset somewhat from the box too, not sure how that's possible, but that's what it looks like from the small hole I have opened up to see inside the wall. I hope I can get the hole expanded enough evenly without expanding it too much - I'm a bit worried about that as it is plaster.
You should be able to cut the nails holding the existing bracket through a 1" slot that's only wide enough for a hacksaw or sawzall blade - too narrow to see through. I cut old boxes out using the Braille method - no vision, touch only.
 
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Old 08-02-12, 04:12 AM
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I'm going to have to expand the hole a fair amount to even get to the nails holding the existing box in.
Do you mean like the one below.

If so you just make a saw cut against the stud going high enough and low enough to cut the nails so you can push it back into the wall cavity. Tape a couple of feet of string to each cable to be sure you don't loose them when you pus the box into the wall. No harm leaving the box in the bottom of the stud space. Then you just have the saw cut to patch.

Tip first slide the freed box up, especially if you have cables from below. Retrieve those cables and bend them over the Sheetrock before pushing the box down.
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Last edited by ray2047; 08-02-12 at 05:50 AM.
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Old 08-02-12, 11:53 AM
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Do you mean like the one below.
Yes, that looks about right as far as I can tell. I'll try those suggestions; thank you.
 
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Old 08-02-12, 12:46 PM
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Just noticed you said the wall was plaster not Sheetrock. A Sawzall with a wrecking blade will make it a lot easier then trying to do it by hand. Just be sure to hold the saw far enough away from the wall you don't punch through the wall on the other side.
 
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Old 08-02-12, 06:36 PM
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I finally got the old box out. I couldn't get to the nails through the straps with a hacksaw blade because they were in too tight to fit the blade between the stud and the strap and between the strap and nail head. Ended up having to cut through the straps where they angle in towards the box. Took awhile but finally got through both of them.

I tried prying the box away from the stud with a pry bar, and it bent the box out some - which helped in cutting the straps - but didn't do anything to budge the nails. I probably could have if I would have pried farther, but it was messing up the drywall. Turns out it's drywall after all. Two layers of it, a 1/2" layer covered up by a 5/8" layer.

Once I got the straps cut I couldn't get the box loose from the cables. I probably could have easily enough if there were just 2 running up from either the top or bottom, but with 2 going through the top and 1 in the bottom and no room to get my hand in there to pull them out, it just wasn't working. Ended up tilting the box enough to remove the screws in the sides of the box to get the side panels out, and then I was able to maneuver the remaining part of the box frame enough to get the cables out. What a pain.

I had to enlarge the hole a little more to the dimensions of the new box and decided to call it a night after that. I tied all the greens, whites, and blacks together with wire nuts for overnight. By the way, the non-working outlet in the other bedroom started working again once I connected cable A.

Any tips for running the wires into the new box? Can I punch out the tabs entirely, or is it really necessary to leave them attached on one end? I know it's recommended to leave them on in case anyone ever yanks on the cables from up in the attic, I just don't feel like wrestling with getting the wires into the box any more than is absolutely necessary.
 
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Old 08-02-12, 07:39 PM
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You have just learned the three most important rules when doing this kind of work. Improvise. Revise. Improvise. Well done!

The tabs are cable clamps and should be left in place. Before inserting the box tap each you will use loose with a hammer and screwdriver. They will hinge in on one firmly attached side.

Turns out it's drywall after all. Two layers of it, a 1/2" layer covered up by a 5/8" layer.
That could be a problem. The boxes aren't usually made to work in that thick of a wall. You may either have to use longer screws or Madison clips. The picture below shows typical use but you should also be able to use them with a plastic old work box.

the non-working outlet in the other bedroom started working again once I connected cable A.
We knew that but we wanted to surprise you with that.
 
  #33  
Old 08-03-12, 07:41 AM
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I'm not entirely sure I understand the details of using an F clip. In fact, I'm quite sure I don't. It sounds simple enough - one part goes in the wall, and the other parts fold over the box. For some reason, I'm having difficulty mentally picturing the "inside the wall" portion. Do you happen to have a picture of one after it's been folded over? I tried searching online for more info about them but couldn't find the type of picture I was looking for.

I'll probably just try longer screws though, so if you don't have a picture like that readily available don't worry about it.

If I do need to use the clips, any idea if places like Lowe's, Menard's, Home Depot carry them? Or would I need to go a more dedicated electrical store?
 
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Old 08-03-12, 08:21 AM
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Check first to see if the box ears can be retracted back far enough to work. Madison clips might not be code compliant with a plastic box because of grounding safety so I retract my original suggestion to use them. See: box hanger

A plan "C" would be to break away just enough of the inner Sheetrock layer so the clips will rotate up and grab the outer layer.
 
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Old 08-03-12, 09:44 AM
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While I hadn't thought of the grounding issue that Ray brought up, I also hadn't thought of using Madison straps (Madison clips, F clips, etc.) to mount a plastic old work box. I agree with the information Ray found that concluded that this combination shouldn't be used.

That said, if the screws in your plastic old work box can be backed out to 1-1/8" without losing the ears, then you are good to go. If not, a different "plan 'C'" is to use a metal old work box and a pair of Madison straps. So...
I'm not entirely sure I understand the details of using an F clip. In fact, I'm quite sure I don't. It sounds simple enough - one part goes in the wall, and the other parts fold over the box. For some reason, I'm having difficulty mentally picturing the "inside the wall" portion.
F clips are bought and used in pairs. They are installed tight against each side of the box, outside it. The long straight piece goes inside the wall. Very importantly, the longer end needs to point up and the shorter end down, to have it hold reliably. The two shorter legs point out. They are bent into the interior of the box and crimped tight.
Do you happen to have a picture...
If you scroll down toward the bottom of the page Ray linked to, there's an illustration... OK, got it:

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And yes,
places like Lowe's, Menard's, Home Depot carry them
 
  #36  
Old 08-03-12, 11:10 AM
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You could also try to install a Smartbox that screws to the studs. You might need a box extender so the screws catch the stud and the box face is flush with the drywall.
 
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Old 08-03-12, 11:43 AM
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PCBoss sugested:
You could also try to install a Smartbox that screws to the studs.
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  #38  
Old 08-03-12, 04:36 PM
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F clips are bought and used in pairs
We always called them, 2 men in a boat!
 
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Old 08-03-12, 06:14 PM
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Wow, thank you all for all of the helpful information! I got busy tonight with other projects, so I'll be picking this back up tomorrow to try to get it done. I'm going to try using the clips on the box first. Hopefully I won't have to resort to using F clips or a Smart box.
 
  #40  
Old 08-03-12, 07:10 PM
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We always called them, 2 men in a boat!
And we always called them battleships!
 
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