A stair lift is a mechanical device for lifting people, typically those with disabilities, up and down stairs. For sufficiently wide stairs, a rail is mounted to the treads of the stairs. A chair or lifting platform is attached to the rail. A person gets onto the chair or platform and is lifted up or down the stairs by the chair which moves along the rail. Stair lifts are known variously as stairlifts, stair-lifts, chair lifts, stair gliders and by other names. This type of chair lift should not be confused with the chairlift used by skiers. The term stair climber can refer either to stair lifts, or more commonly to the exercise equipment by the same name. Some of the first stair lifts to be produced commercially were advertised and sold in the U.S. in the 1930s by the Inclinator Company of America. Many users at the time were victims of polio. Now they are seen for use in elderly, fall-prone individuals, and disabled people who are unable to navigate stairs safely. History In the 1920s, C.C. Crispen, a Pennsylvania entrepreneur, created a way to enable his ailing friend to travel from floor to floor. Crispen's idea was to design a seat that could climb stairs. A self-taught engineer, he built the first prototype of the inclining chair. He called it the Inclin-ator. Prior to this Frederick Muffett of Royal Tunbridge Wells, invented and patented the "An Invalid Chair with Tramway for use on Staircases". However, TV historian Doctor David Starkey has in 2009, found evidence in a list of the possessions of King Henry VIII that attributes the first stairlift invented to the monarch. The 30 stone (190 kg) king, injured through jousting, used a chair that was hauled up and down stairs on a block and tackle system by servants at the ancient Whitehall Palace in London. Features Modern stair lifts can be found with a wide variety of features such as adjustable seat height, battery isolation switches, call stations, 'flip-up' rail, key switch, folding step, speed governor, seat belt, soft start and soft stop. Rails Straight rails for use on domestic staircases are usually made from extruded aluminum or steel and come in various cross-sectional shapes. These rails may, typically, weigh over , depending on the length. In most applications they are attached to the steps with metal brackets (sometimes called "cleats"). If a rail crosses