Roof and tunnel hacking is the unauthorized exploration of roof and utility tunnel spaces. The term carries a strong collegiate connotation, stemming from its use at MIT and at the U.S. Naval Academy, where the practice has a long history. It is a form of urban exploration. Some participants use it as a means of carrying out collegiate pranks, by hanging banners from high places or, in one notable example from MIT, placing a life-size model police car on top of a university building. Others are interested in exploring inaccessible and seldom-seen places; that such exploration is unauthorized is often part of the thrill. Roofers, in particular, may be interested in the skyline views from the highest points on a campus. On August 1, 2016, Red Bull TV launched the documentary series URBEX – Enter At Your Own Risk, that also chronicles roof and tunnel hacking. Vadding Vadding is a verb which has become synonymous with urban exploration. The word comes from MIT where, for a time in the late 1970s, some of the student population was addicted to a computer game called ADVENT (also known as Colossal Cave Adventure). In an attempt to hide the game from system administrators who would delete it if found, the game file was renamed ADV. As the system administrators became aware of this, the filename was changed again, this time to the permutation VAD. The verb vad appeared, meaning to play the game. Likewise, vadders were people who spent a lot of time playing the game. Thus, vadding and vadders began to refer to people who undertook actions in real life similar to those in the game. Since ADVENT was all about exploring tunnels, the MIT sport of roof and tunnel hacking became known as vadding. Today, the word vadding is rarely used at MIT (usually only by old-timers) and roof and tunnel hacking has returned as the preferred descriptive term. Those who participate in it generally refer to it simply as "hacking". Roof hacking Many buildings at American universities have flat roofs, whereas pitched roofs designed to shed snow or heavy rain present safety challenges for roof hackers. Entry points, such as trapdoors, exterior ladders, and elevators to penthouses that open onto roofs, are usually tightly secured. Roofers bypass locks (by lock picking or other methods), or use unsecured entry points to gain access to roofs. Once there, explorers may take photographs