The bays are first completed, after which the traverses begun by No. 4 rear rank are finished up. Great care should be taken to make the dimensions of the trench as accurate as possible. The squad leader is held responsible for this. He should provide himself with two sticks. On one the following lengths are laid off: 1 foot, width of berms, and height of parapet; 1 foot 4 inches, width of firing banquet, height of firing banquet above bottom of trench, and width of bottom of trench. The other stick has the following lengths measured on it: 4 feet, depth of trench from ground surface to the top of firing banquet; 5 feet 4 inches, depth of trench from ground surface to bottom of trench. (See Plate 15 for dimensions of standing trench.) When the circumstances are such that the work of trench construction is interfered with by the enemy, a modification of the system outlined here will have to be made, but the details should be adhered to as closely as possible. When night work is necessary the trace should be staked out before complete darkness sets in. If the trace can only be made after dark, visible reference points needed with white paper, white tape or screened flashlights may be utilized. Stick to the details of the deployment, the laying out of tasks and the procedure as indicated for day work as closely as possible. Avoid making any more noise than is absolutely necessary; allow no smoking and require such conversation as is necessary to be made in whispers. Protect the workers by a system of patrols to the front. Non-commissioned officers are held responsible for a systematic and orderly execution of the work being performed by their units. The captain cannot be everywhere along the line. He has to depend upon the platoon and squad leaders in the work. That is why you should study it and know about it so as to be able to make good when the time comes. CHAPTER VIII GRENADE WARFARE The use of hand grenades as an implement of warfare dates back many centuries. History records their use as far back as 1536. Up to the close of the eighteenth century soldiers were trained in the throwing of hand grenades, and for this reason were called "grenadiers." At first there were a few in each regiment, later entire companies were formed, and finally each infantry unit that corresponds to our battalion of today had its own grenadier unit. Then there was a period of time when more open formations were adopted, when there was less opportunity for the employment of grenades and their use was practically eliminated from the battlefield and confined to sieges, where they have been used more or less since the dawn of military history.