Although wrestling, because of its sporting heritage, is void of submission holds or "choke" holds, it has an impressive array of take-downs and control techniques. Wrestlers also learn to be alert to the location and positioning of an opponent in relation to his own body. This is achieved mostly through touch rather than sight, which means familiarity with wrestling techniques can provide an officer with an advantage in dark or poorly lighted areas. In contrast to wrestling techniques, jiu-jitsu does have submission holds and "choke" holds. Most of these techniques do not cut off the opponent's breathing, but rather restrict blood flow to the brain for their effect. Jiu-jitsu stylists are familiar with the "tap-out," a term for tapping an opponent or the mat when an opponent's submission hold is so tight that further pressure will cause damage or when a choke applied any longer will cause loss of consciousness. In training, officers learn the time frames and physical symptoms that they will experience if an opponent traps them in a potentially dangerous hold. It is at this point that an officer must end the fight or lose consciousness. Drawing a firearm and contact shooting the attacker, if possible, may be a valid option at this point. A pocket knife, if available, may also be useful in such a situation. Attempting to struggle more strenuously against the hold may only hasten unconsciousness or cause severe injury that incapacitates the officer.