Unlike screws and nails, which get their holding power from wood fibers, bolts draw their might from their own steel shafts. Holes have to be drilled first so the bolt's shaft slides into the hole. The bolt is held in place by a nut that is screwed on from the back. Because of their unsurpassed strength, bolts are used for assembling things that will carry weight — from picnic tables and outdoor furniture to wooden decks.