Nesting-Long-Grain-Miter-Joint Published January 28, 2013 at 370 × 328 in Specialized Router Bits: Finger Joint Bits Add Strength to Miter, Plywood and Sheet Good Joinery Miter joint end grains glue very poorly, but adding a fingerjoint to the ends of the miter adds surfaces for glue-ups, allowing them to hold fast and strengthen the joint considerably.