There's no better way to align, glue, and clamp 45° and 90° angles whether it's prefab production of window and door casings or one picture frame. Miter Cats are made of solid urethane and use screws to fasten them to the backside of casing, picture frames, or trim, setting up a perpendicular clamping path to squeeze miter joints tight. Use with or without biscuits. Will not leave holes or mar the finish surface. Only one clamp of almost any style is necessary for each joint. For 90° angles on casings up to 2-1/2" wide, choose a clamp with at least a 6" opening length. For 45° angles on casings up to 2-1/2" wide, choose a clamp with at least a 12" opening length. For wider casings, you may need a clamp with greater opening length.