some of the benefits of skateboarding as an alternative to automobiles. Military The United States Marine Corps tested the usefulness of commercial off-the-shelf skateboards during urban combat military exercises in the late 1990s in a program called Urban Warrior '99. Their special purpose was "for maneuvering inside buildings in order to detect tripwires and sniper fire". Trampboarding Trampboarding is a variant of skateboarding that uses a board without the trucks and the wheels on a trampoline. Using the bounce of the trampoline gives height to perform tricks, whereas in skateboarding one needs to make the height by performing an ollie. Trampboarding is seen on YouTube in numerous videos. Swing boarding Swing boarding is the activity where a skateboard deck is suspended from a pivot point above the rider which allows the rider to swing about that pivot point. The board swings in an arc which is a similar movement to riding a half pipe. The incorporation of a harness and frame allows the rider to perform turns and spins all while flying through the air. Controversy Skateboarding damages urban terrain features such as curbs, benches, and ledges when skateboarders perform "grinds" and other tricks on these surfaces. Private industry has responded to this problem by using skate deterrent devices, such as the Skatestopper, in efforts to prevent further damage and to reduce skateboarding on these surfaces. The enactment of ordinances and the posting of signs stating "Skateboarding is not allowed" have also become common methods to discourage skateboarding in public areas in many cities, to protect pedestrians and property. In the area of street skating, tickets and arrest from police for trespassing and vandalism are not uncommon. Skateboarding has become an important problem in Freedom Plaza, a National Park within the Pennsylvania Avenue National Historic Site in Washington, D.C. The Plaza has become a popular location for skateboarding, although the activity is illegal and has resulted in police actions. The Plaza contains copies of portions of Pierre (Peter) Charles L'Enfant's 1791 plan for the nation's capital city that have been inscribed in the park's raised marble surface. A 2016 National Park Service management plan for the Historic Site states that skateboarding has damaged stonework, sculptures, walls, benches, steps, and other surfaces in some areas of the Plaza. The management plan further states that skateboarding presents a persistent law enforcement and management challenge, as popular websites advertise the Plaza's attractiveness for