C-clamps range in size from 1 to 8 inches long, with throat depths from 1 to 3 1/4 inches (although special deep-throat C-clamps also are available). They're essential for small- and medium-size gluing jobs and a variety of other holding tasks. Home Improvement Encyclopedia
The C-clamp or G-cramp is a type of clamp device typically used to hold a wood or metal workpiece. These clamps are called "C" clamps because of the C shaped frame and are often used in, but are not limited to, carpentry and welding.