If in the first act you have hung a pistol on the wall, then in the following one it should be fired. Otherwise don't put it there.
In 1889, Ilia Gurliand noted these words from a conversation with Chekhov (see Donald Rayfield, Anton Chekhov: A Life, New York: Henry Holt and Company, 1997, p.203). Chekhov repeated this point a number of times.
