Another penalty may be the need to contact somebody, with the penalty being having to explain what has happened. Many release mechanisms are used in self-bondage to allow the practitioner to escape the restraints after a period of time. There are various trade-offs to be made between ease of use, reliability, precision of timing, cost, and so forth. There should be several mechanisms available, thus ensuring redundancy and safety. There are also a number of release mechanisms designed to be emergency backups. The idea behind these release mechanisms is that triggering them will cause something undesirable to happen, and thus are only used in situations where death or serious injury could occur otherwise. Apart from release mechanisms, self-bondage poses a somewhat awkward problem of getting "into" bondage, especially when using rope. What might be a relatively simple matter for couples can be considerably more complex alone. With rope, the main difficulty is tying the hands in a way that is not easy to untie. One common solution is to use a "cinch noose" — essentially a kind of slip knot — together with a "coil" (a loop of rope). The wrists are placed through the coil with the cinch noose between the wrists and around the coil. To achieve a basic hogtie position, the cinch noose is tied to the ankles. With pressure, the noose tightens the wrist coil, securing the hands. It proves very difficult to escape from, and usually a knife or scissors is required to cut free. Equipment that can be tightened only, and not loosened, often has application in self-bondage. This includes handcuffs, zip ties and ratcheting pulleys. While for the most part self-bondage is performed using ordinary and easily available equipment (indeed, it lends itself to impromptu adaptation and a "do it yourself" approach), a few commercial products have appeared — in the United States and United Kingdom for the most part — catering for the self-bondage practitioner.