A cut made in the face of a heading for which three or four holes are drilled normal to the face and in a triangle or square, 12 to 18 in (30.48 to 45.72 cm) on a side, with another hole in the center. One, two, or three holes are loaded and shot; the others relieve the pressure and induce breaking. A cavity is formed to which other shots in the face readily break. Used for esp. tough ground.