Take the frustration out of frame joints with this convenient clamp. Spring-loaded jaws transfer clamping pressure directly to the joint. The large ergonomic knob easily tightens jaws onto frames 5/8" to 2-7/8" wide. Back jaws adjust up to 1° to ensure a perfect fit if joint is slightly out of square. Open design allows easy access to outside corners and back surface for simple mechanical fastening. Swiveling Base (sold separately) features a matching hole pattern to easily mount the clamp, elevate your work and gain improved work angles for access to outside frame edges. Frame Clamp is made of lightweight cast aluminum Swiveling Base is made of solid steel