Ratchets in combination with sockets are used to quickly turn nuts and bolts. A ratchet is basically a lever with a pivoting mechanism, which allows the user to tighten or loosen a fastener without removing the tool. Ratchets are sized according to the square driver head. For example, 1/4″ drive ratchets have driver heads that are 1/4″ x 1/4″. Common ratchet sizes are 1/4″, 3/8″, and 1/2″. A 3/8″ ratchet is the most common size found in a basic tool kit.