A ritual gesture of contrition whereby one makes of fist of the right hand and strikes it against the left breast, firmly but without making a loud thump.

This is done at three points in the mass:

• During the Penitential Rite - three times at "by thought, word, and deed"

• At the Agnus Dei - at each of the three "sins of the world"

• At the Domine, Non Sum Dignus - at each of the three "I am not worthy"