Richards and Joseph Bardsley also played important parts in the development, improvement and commercialization of door closers along with other companies, including Yale, Norton, Rixson and The Shelby Spring Hinge Company. Since the 1970s/1980s Dorma and GEZE have pushed to dominate the door closer business, with Ingersol Rand, ASSA ABLOY, RIXSON having large portions of the American market. Types There are seven styles of interior door-closer: Surface-mounted Concealed in frame (jamb) Concealed in header (transom) Concealed in floor Concealed in door Concealed in shoe Integral to hinge Spring Hinge Self-Closing Hinge Overhead or surface-mounted door closers come in four variations: slide-track arm, regular arm surface mounted, parallel arm surface mounted, and top jamb mounted, most are surface mounted although some manufacturers offer concealed models too. Another type of surface mounted door closer is attached to the door frame behind the door (where the hinges are) next to the middle hinge. The "arm" (tail) rests against the door, and a spring that is twisted by the user opening the door closes the door by returning to its pre-twisted shape. This type of door closer is referred to as a "tail" spring and is one of the more simple mechanisms, having no damping control. There is also the storm door and screen door variation of the door closer: As the name implies, these piston type closers are used on storm doors, security, and screen doors which give the home an extra line of defense against weather, intruders, and insects. Whereas interior closers typically use hydraulics, storm door closers are more typically pneumatic, using air and springs to close the door. Storm door closers often have a small metal square washer on the rod that is used to lock the closer in the open position if required, more recent models have a button to actuate the hold open feature to make this process easier. Concealed, jamb-mounted type door closers, mounted in morticed recesses in the door and door frame, are concealed when the door is closed. These are available in controlled and uncontrolled versions, selected according to the application for which they are intended. Such concealed closers when mounted inside a pocket in the door frame (door jamb) are commonly known as "perco's" or perkomatic closers When door closers are mounted in the header they are known as transom closers. These can be HO (hold open) or NHO (none hold open). Door closers