A set screw is a unit of hardware designed to fasten one object inside of another. The set screw prevents relative movement between the two objects, which allows each to function as intended. These screws are generally made from brass ,carbon steel or stainless steel, and are designed to pass through the outer object and rest against the inner object without passing through.
Set screws are generally fastened using an internal mechanism rather than a traditional external head. The top of the screw may be slotted for use with a screwdriver, or may have a hexagonal shape. Slotted screws are simple to use, and do not require any special tools. Hexagonal set screws can be subjected to greater torque for a tighter connection, but require the use of special tools such as Allen wrenches.