How to Choose the Right Bolt

Consider a lag bolt for heavy-duty fastening of wood to wood or metal to wood.

Use machine bolts and machine screws for metal work. Machine bolts have a hexagonal or square head; machine screws have a slotted head.

Join metals with a stove bolt. This bolt also has a slotted head.

Fasten wood objects with a carriage bolt. This type has a round head with no slot and is sunk up to the "shoulder," a squared-off part on the shank that prevents the bolt from turning once it's in the wood.

Cut a piece of all thread, or threaded rod, to the length you need if you can't find a long enough bolt. Bolts run up to 6 inches long, whereas all thread comes in 3-foot lengths.