Nuts,bolts, and screws join materials together?
Mechanically, using friction, temporarily. Nuts bolts and screws are mechanical elements that work due to friction, but they can be removed to disassemble what ever you are bolting or screwing together… and sometimes they unscrew them selves due to vibration.
—
Mechanically. A screw or nut/bolt is an instance of an incline-plane, which is a simple machine.
—-
Mechanically, using friction. The incline plane of the threads allow the materials to be joined, and friction holds the threads in place so the materials are held together.