PARALLELS, OR PLACES OF ARMS, in a siege, are deep trenches, 15 or 18 feet wide, joining the several attacks together; and serving to place the guard of the trenches in, to be at hand to support the workmen when attacked. There are usually three in an attack: the first is about 600 yards from the covert-way, the second between 3 and 400, and the third near or on
the glaci. It is said they were first invented or used by Vauban.