them to enjoy the Boardwalk. Soon, many healthy tourists also rented the decorated "rolling chairs" and servants to push them as a show of decadence and treatment they could never experience at home. Modern wheelchairs In 1933 Harry C. Jennings Sr. and his disabled friend Herbert Everest, both mechanical engineers, invented the first lightweight, steel, folding, portable wheelchair. Everest had previously broken his back in a mining accident. Everest and Jennings saw the business potential of the invention and went on to become the first mass-market manufacturers of wheelchairs. Their "X-brace" design is still in common use, albeit with updated materials and other improvements. The X-brace idea came to Jennings from the men's folding "camp chairs / stools", rotated 90 degrees, used in the outdoors and at the mines. Types There are a wide variety of types of wheelchairs, differing by propulsion method, mechanisms of control, and technology used. Some wheelchairs are designed for general everyday use, others for single activities, or to address specific access needs. Innovation within the wheelchair industry is relatively common, but many innovations ultimately fall by the wayside, either from over-specialization, or from failing to come to market at an accessible price-point. The iBOT is perhaps the best known example of this in recent years. Manual self-propelled wheelchairs A self-propelled manual wheelchair incorporates a frame, seat, one or two footplates (footrests) and four wheels: usually two caster wheels at the front and two large wheels at the back. There will generally also be a separate seat cushion. The larger rear wheels usually have push-rims of slightly smaller diameter projecting just beyond the tyre; these allow the user to manoeuvre the chair by pushing on them without requiring them to grasp the tyres. Manual wheelchairs generally have brakes that bear on the tyres of the rear wheels, however these are solely a parking brakes and in-motion braking is provided by the user's palms bearing directly on the push-rims. As this causes friction and heat build-up, particularly on long downslopes, many wheelchair users will choose to wear padded wheelchair gloves. Manual wheelchairs often have two push handles at the upper rear of the frame to allow for manual propulsion by a second person, however many active wheelchair users will remove these to prevent unwanted pushing from people who believe they are being helpful. Everyday manual wheelchairs come in two major varieties, folding or rigid. Folding chairs are