A device for cutting a sheet rock panel. A base plate has a through slot that receives a blade of a conventional utility knife and a free end right angle metal end clip of conventional tape ruler and a blind slot that receives the conventional tape ruler. A clamping plate is displaceably attached to the base plate and clamps the conventional tape ruler between itself and the base plate. The clamping plate has a center portion that is circular-shaped and a portion that has a concave upper surface and a convex lower surface that clamps the conventional tape ruler in the concave blind slot in the base plate.