I picked up a couple of 36" Back-To-Back clamps at a garage sale yesterday.
I used one as a basic saw guide and it worked great.

The seller is/was selling all of these:

Single sided includes 2 -- 24"; 1 -- 36" and 1 -- 50".
Double sided includes 2 -- 18"; 2 -- 36" (mine now) and 2 -- 50" clamps

http://i.imgur.com/vjK8vfH.jpg

Asking prices start at $30 for the 50" Back-To-Back down to $13 for the 24" single side. I know he will come down in price: He wanted $36 for the
pair I bought, I paid $30. Those are decent prices, right?

I understand the differences between the Back-To-Back vs. the single side,
but here is what I am curious about:

Are these clamps strictly for use as straight edges or can they be use for
glue ups, such as for panels or cabinet doors?

Is there anything else I should think about before dropping some more
money on the clamps?

Thanks!