Chicago screws are like rivets, but no setting tools required. Use a leather punch to make a hole (3/16" or 5 mm) through all of your layers, pop the front and back through the hole, and screw together. Done! Recommended for thicknesses of 1/4" (6 mm) (Medium) and slightly thicker, and 3/8" (10 mm) for Large.
Note: Use "Loctite" to secure if needed.
3/8" x 1/4" long