A gallows, in the ordinary sense, is scarcely intended, since hanging was not a Persian punishment. The intention, no doubt, was to crucify (see the Esther 2:23 note) or impale Mordecai; and the pale or cross was to be 75 feet high, to make the punishment more conspicuous.
Speak thou unto the king ... - Requests for leave to put persons to death were often made to Persian kings by their near relatives, but only rarely by others.