FOR USED PLATENS. Vertical Clamp with 0 – 20 inch clamping envelope and 4-1/2 inch throat. Round Knurled boot fits 1-1/2″ square hole typical of some old, used Platens. Simply drop this clamp into a square hole, tilt it back, slide the arm down until swivel pad contacts your work piece, and turn the screw. You will be securely clamped in seconds. Clamp can usually be loosened, and swivelled out of the way, when you are finished your welding or work process. Super simple and very fast clamping (and unclamping) process.