The first rule of inventing might be: no matter how commonplace a device is, someone will always think of a way to improve it. Take, for example, award-winning industrial designer Larry Laske's new beach chair. It's basically a chair backrest molded in plastic with two spikes to anchor it in the sand. Laske filed a U.S. application in 2004 and was awarded a patent in 2007 (7178875B2). According to the patent, Laske's intent was to create a chair that is "lightweight, easy to carry and simple to use." You can buy them in blue, green, yellow and orange on Laske's website www.beachthingy.com. With the exception of the elimination of one of the handholds, the finished product is identical to the patent drawing.
The beach chair has been reinvented many times over. One of the earliest patents, which the patent examiner cited in his review, was issued in 1919 (1312774).