Shoulder socket screws are a type of headless screw that has a cylindrical shank with a shoulder or step. The shoulder allows the screw to be inserted into a pre-drilled hole and then tightened against a flat surface, providing a secure and aligned connection. Shoulder socket screws are commonly used in applications where precise alignment and a clean, finished appearance are required. They are often used in machinery, furniture, and other applications where a flush or nearly flush finish is desired.