Corner Cutters are cut from clear 1/8" acrylic (paper still affixed for better pictures). A lovely lady suggested the "cut in" sections in the corner and this concept allows the 45mm blade to cut to the inside corner, even with 2 (two) layers of fabric, which allows you to cut more than 1 (one) corner at a time, for even more time saving.
Corner Cutter JR cuts box corners 1", 1 1/2", 2" and 2 1/2" corners.