A submission, also called a "tap out" is a combat sports term for yielding to the opponent, resulting in an immediate defeat. A submission is often performed by visibly tapping the floor or opponent with the hand or foot, or by verbalizing to the opponent or referee of the competition. In combative sports where the fighter has cornermen, the cornerman can also stop the fight by "throwing in the towel" , which may count as a submission. To force a submission a fighter must do a submission hold, of which there are two categories. The first is a joint lock, which can include armlocks, americanas, anklelocks, kneebars, etc. These submissions damage the joints by hyperextending and threatening to break them. Secondly there are chokeholds. These include the rear naked choke, guillotine choke, triangle choke, etc. These prevent air flow to the lungs or blood flow to the brain, risking the fighter to go unconscious.