Frame Building Course

The method we used was very easy(that easy know one in the group guessed, I was going down the clamp and surface table route!), hold two tubes together on the work bench and mark each end with a marker where they touch.

That's a really good technique if you don't have the clamp and table.

That's how I do it, clamp the tube to the plate, run an engineer's square along the length, let the thin steel edge make a nice light mark along the tube.