Carriage bolts connect metal components to metal components or metal components to wood. To prevent spinning when the nut is fastened, they have shallow semi-round heads and either a square or ribbed (ridged) neck under the head. The design of step bolts, which bolt down wood to wood surfaces, is similar to that of a carriage bolt. Step bolts, on the other hand, feature a circular head with a wider, lower-profile profile. Step bolts are preferred for wood connections (such as decking) because the bigger diameter head of the step bolt will not pull through soft wood.