The BEST Corner Key Kit includes a set of four keys that can be used on wood stretcher bar frames or other bars such as the . You should mount the keys by using the pre-drilled holes on the or by making your own in wooden bars with a 3/32" drill bit. You can also power drive the keys in with a drill screwdriver bit. Use a punch tool to start the hole for best results if not pre-drilling.The BEST keys are an essential tool for adjusting the tension of your canvas material just by the turn of a nut!