Keisaku

In Zen Buddhism, keisaku (Japanese; kyosaku in the Soto school) is an attempt by a sensei to alert students to their mindlessness in zazen (sitting meditation), usually administered by a stick. An English translation is stick of compassion.

In a more colloquial fashion, a keisaku is a "reality check", or something that alerts one to further contemplate their situation, in order to understand and work things out.

Keisaku is always administered at the humble request of the student, by way of bowing one's head and putting the palms together, and then exposing each shoulder to be struck in turn. It is not a punishment, but a self-administration by proxy, as it were.

Keisaku sticks occur only in Zen, not in other Buddhist schools such as Theravada, Mahayana, or Nichiren.