The War of Rebellion, O.R.A., Series I, Vol. XXV, Part II, 151
Special Orders, Headquarters Army of the Potomac,
NO. 79. March 21, 1863
"........ In the batteries of light 12-pounders, it is very important that the the fuse be screwed down tightly, so that the horseshoe on the bottom may be supported by the shoulder of the fuse-hole. If this is not done, a premature explosion may result. The fuse-wrench furnished with the battery stores, is used for this purpose, and, when practicable, the fuse should always be screwed down just before firing.
By Command of Major-General Hooker
S. Williams
Assistant Adjutant-General"