No more measuring, creating templates or guesswork when installing fasteners with Keyhole Companion. It solves the problem by attaching to keyhole slots and marking where on the surface fasteners should be installed. The deepened marking pad ensures that the surface remains free of unwanted marks when positioning the object. Durable black and white ink will make over 1000 highly visible marks on both light and dark hard, soft, smooth and rough surfaces. Works with most types of keyhole openings, including cast, mortise and hinged devices, and is suitable for thicknesses from thin metal to 3/8 inch. Commercial grade construction utilizing internal metal components offers strength and durability.