Single Whip is a common posture found in most forms of tai chi chuan. Typically at the end of the posture the left hand is in a palm outward push and the right hand held most commonly in the form of a hook or closed fist. Notable exceptions are the Single Whip in and Wu/Hao style tai chi chuan which finish with both hands open, palms outward.
Single Whip is one of the movements/postures most repeated in the solo training forms. Its first appearance in most forms follows the Grasp Sparrow's Tail sequence and is seen later as a variant renamed Snake Creeps Down. There is also a posture in the form called Single Whip Fusing Throat.
The martial applications of Single Whip are many. There are various strikes, throws, changeups and kicks derived from this posture trained by different schools.