I would like to know the steps involved in cutting the top of a new fence straight. This is a fence on a slope with the boards installed and would like to cut a given section roughly parallel to the ground but more importantly, completely straight. That is, no matter how taught a mason line is made, it always has some over 50ft, or even 20ft. A laser seems less than useful because it is less than visual over 20ft outside unless one starts in after the sun goes down. Tricks of the trade anyone?

 

You use a chalk line. Mason's lines have no chalk. Pull it as tight as you can get it without breaking the line, then have someone go it the middle, push the line up about 1/8" to account for minimal sag , hold it down with one finger, and snap each side.

Or put a nail in each side, pull it tight, wrap it up so it stays and go in the middle and snap it yourself.

Chalk has a variety of levels of permanence. You want 0 permanence. It will say on the label.

Fence guys would generally put up a few pickets here and there along any major changes in the grade, then stretch the Mason's line across the top, and then hang all the fencing to that line. Minimal cutting that way.

 

If the change in slope around the perimeter of the fence is almost the height of the fence, the narrow sections won't look pleasing to the eye in my opinion.

 

I am sure the change in grade between any 2 fence posts or your ability to saw a flat cut, even with a guide, is much greater than the droop of a tight caulk line between the same 2 fence posts. Are your pickets plumb vertically?