The supplied Double Clamps - C- Clamps are 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. C clamps can keep pieces of wood and metal together to help you drill straight holes or cut at a straight angle. Double Clamps - C- Clamps are also great when you need to press on two pieces of material to ensure they stick together when using an adhesive.