Recently, I had the need to clamp the two sides of a drawer. Since I don't own bar or pipe clamps, the only clamps to use were the popular quick clamps that have the squeeze-handle triggers and padded clamp surfaces.
The problem was that one clamp was not wide enough to extend outside the drawer sides. The solution was to extend two clamps just over half the width of the drawer. Then I lined the clamps up so the trigger handles were outside the drawer (on opposite sides of each other) and the other ends were inside the drawer.
The trick was to interlock the ends of the clamps that were inside the drawer so the clamping surfaces were pulling flat against each other toward the outside of the drawer. A couple of squeezes on the handles and I had one great clamp that was made of two.