Shoulder screws, also known as shoulder bolts, have threading only part way up the screw and then a smooth shaft close to the head to act as a spacer or bearing. The shaft is generally longer than the thread of the screw, and the point is blunt. Shoulder screws with round shafts are commonly used for items that require rotation, while those with square shafts are used to lock into place and prevent rotation. They are often used in mechanical or automotive applications. The length indicated for a shoulder screw denotes the length of the shoulder not including the head height or threaded length.