The Low Hammerfist Target Strike is a hammerfist strike in which the off-hand serves as a target. The target hand is shaped like a knifehand; it is held below the belt with the arm straight. The hammerfist strikes the target with the palm of the fist facing away from the body.
The Low Hammerfist Target Strike is used in the form Koryo, for example. In Koryo, bring both hands down in a circular motion with your left fist striking your open right palm at the bottom of this circle.