Binding barrels (AKA sex bolts or Chicago screws) clamp things together. They are two-part systems consisting of a flanged, internally threaded barrel that runs the length of the hole and a machine screw which threads from the other end of the materials to be fastened. Size considerations: diameter/thread size, barrel length, thread size, and barrel diameter. Other variables: head style, finish, drive type and material. Many people who view this item also view our selection of machine screws.