A roll cage is a specially constructe frame built in or around the cab of a vehicle to protect the occupants from being injured in an accident, particularly in the event of a roll-over. Roll cages are used in nearly all purpose-built racecars, and in most cars modified for racing. There are many different roll cage designs depending on the specifications of the sanctioning body. Roll cages are built to extend the frame in front of the driver, next to the A-pillar, to provide as much high-speed protection as possible in a coupé. This is compared to the protection provided in open wheel racing, where a solid shell encases the majority of the driver's body as well as a rollover hoop that extends over the driver's helmet. A roll cage can also do a great deal to stiffen the chassis, which is desirable in racing applications.