A C-clamp or G-clamp or G-cramp is a type of clamp device typically used to hold a wood or metal workpiece, and often used in, but are not limited to, carpentry and welding.
One end of this screw contains a flat edge of similar size to the one at the top of the frame, and the other end usually a small metal bar, perpendicular to the screw itself, which is used to gain leverage when tightening the clamp.
A C-clamp is used by means of turning the screw through the bottom of the frame until the desired state of pressure or release is reached.
If the clamp is being loosened, this is when a sufficient amount of force is released to allow the secured objects to be moved.
This can be avoided by buffering between the clamp and the timber using two pieces of scrap wood.