The attached image shows a very sturdy black plastic column (2" diameter).
A vertical slot is compressed by two hose clamps. I must use a nut driver
or ratchet handle to adjust pressure on the sliding metal pipe inside the column.

Instead of hose clamps, I'd like to find an adjustable collar with a big knob
or T shaped handle.

I thought the Home Depot plumbing department would have some kind of heavy
duty collar. They didn't. Making a collar with a knob or handle in my shop is
possible, if I can't find this item on the web. The problem is, what do I search for?
Google, "collar with big knob" or something like that.

Collar Dimensions:

2" circumference to fit the plastic column
1⅛" height (or width) minimum - About the same as two hose clamps

This might be the kind of item available from industrial surplus websites. If you
know where to buy an adjustable collar, please let me know.

 

Search for " 2" locking collar clamp ". Some possibles there.

I use these for sound system speaker stands. Collar clamp and telescoping collar. The only problem is these are for 1-1/2" tubing.
planetdj/pro-audio//speaker-stand-parts

 

Or maybe these?

https://www.aliexpress.com/item/2x-D...764026124.html

Or I bet these are pricy...

http://www.normaamericasds.com/produ.../v-band-clamps

 

There are dozens of designs for "2 inch tubing clamps". Google-image it and choose the look & price you like.
My ATV has a 2" rollcage and I've seen all kinds of clamps used to secure lights, speakers, cameras, spare tire, etc...from cheap pipe hangers to expensive polished billet aluminum.

Personally I'd buy a 2" 2-piece shaft collar (online) and replace the cap screws with thumbscrews.

 

Thanks guys.

The collar in the attached image is not 2 inches, but it's close to what I had in mind.

I've built many jigs and fixtures for one project. Usually, they are dismantled for
scrap when the job is finished. This sliding pipe jig is so useful in my shop, I decided
to keep it.

Stainless hose clamps are plenty strong, but constantly loosening and tightening
screws with a nut driver or ratchet is a pain in the neck!

Google images displays a mind boggling variety of collar clamps. I didn't see anything
that would be much better than common hose clamps. It's important that the knob
or handle is very easy to rotate. That's why I said "big knob."

I'll probably have to make the collar myself, if want to keep this sliding pipe jig.