A swivel's a connection that allows the connected object, such as a gun or chair to rotate horizontally and/or vertically. A common design for a swivel's a cylindrical rod that can turn freely within a support structure. The rod's usually prevented from slipping out by a nut, washer or thickening of the rod. The device can be attached to the ends of the rod or the center. Another common design's a sphere that's able to rotate within a support structure. The device's attached to the sphere. A thi… (More on Swivel)