C-Clamps, or G-Clamps, are generally made of metal and are used to hold wood or metal work pieces. The top of the "C" is a small flat edge to enable the screw fixture to put pressure on the upper part of the frame. Turning the screw allows you to apply or release pressure. Deep C-clamps allow you to have more working room when clamping your project. Shop our online selection or contact us today for a custom quote. Our knowledgeable sales team is available to help.