You dont compress a piston with a C clamp, you use a piston ring compressor to compress the rings and tap the top with a hammer to sit it back in to the cylinder bore. The C clamp is used for compressing valve springs. *AArOn*
You can use a large C-Clamp to compress the caliper piston.
Brake piston? Front use a "C" clamp to compress Rear - Piston is threaded turn clockwise to compress (water pump pliers?)
On the fronts, you can use a C clamp to compress the piston but the backs you have to screw the piston in, don't use the C clamp because you will screw it up, they sell the small tool that you use to screw in the piston at any auto parts store.
Shade tree mechanics use a C-clamp and a flat steel bar to compress the piston. I have also used a large adjustable Channel-Lok-type pliers to compress.
Use a "c" clamp to fully compress piston into caliper body
Use a C clamp to push the piston out of the way to remove and also to place back on rotor.
use a c-clamp and push the piston in that way. style c-clamp i sue http://www-ece.rice.edu/~jdw/figs/c_clamp_2.jpg
with a c clamp. put a block of wood or your old pad over the piston and tighten with clamp.
Similar to any other caliper piston, you might used a C-Clamp that has been covered in some protective coating to prevent it scratching the caliper. Ideally the C-Clamp would not directly compress the piston edge but some piece of flat metal, laid out in a way that would allow it to spread the force across the piston's diameter.
use a large c-clamp aiso use the old brake shoe on the caliper piston to squeeze it back in
use a C clamp
If it is the front brake use a "C" clamp to retract piston If it is the rear and the parking brake is used by this caliper piston is threaded and a special tool (not expensive) available at Sears or auto parts to "screw" piston into caliper body