Allusion is thought to be made here to the custom of hanging gates so that, instead of opening in the ordinary way, they rise and fall as they open and shut. A gate of this description was called cataracta, because of the force and noise with which it fell. It was used in the fortification of towns, and corresponded to the portcullis of modern times; and is supposed to have been known in the time of David. See Smith's Dictionary of Greek and Roman Antiquities, s. v. Cataracta.