|Original photo courtesy of Reggie Biala|
Check out Ron Keslar (AKA) as he busts a first round reverse triangle on Eric Lawson. The reverse triangle (i.e., legs locked on the side of the free arm) is used primarily as a crank or compression-type submission or as a transitional position, as opposed to the more common triangle choke, which is a true choke (i.e., stopping blood flow to carotid artery). It's oftentimes employed as an alternative to the triangle choke, if the choke cannot be finished (e.g., your opponent interlocks his arms underneath you or grips his own gis/shorts, preventing the choke).
In the case below, Keslar somehow scrambles/transitions in to this position and sets up shop (a triangle shop), seeking out the armbar that often develops from the triangle position. We say - nice grappling!