A Chicago screw, also known as a binder post or screw post, is a type of fastener that consists of two mating parts: a male screw and a female barrel or post. The male screw has a threaded shaft with a head at one end and a pointed tip at the other. The female post has a hollow bore with a flared end that allows the male screw to be inserted and securely tightened into place.

Chicago screws are commonly used in applications such as knife, bookbinding, leatherworking, and scrapbooking, where they provide a removable and adjustable binding that can be easily disassembled and reassembled. They come in various sizes, materials, and finishes, and can be customized with different types of heads and lengths to meet specific requirements.