6. The parapet should be so sloped that there is a maximum grazing fire when the rifle is fired as it lies on the parapet. To insure that the bullet will not graze the parapet, although the sights are clear, look through the barrel with the bolt removed. COMMUNICATION TRENCH In the first line fire trenches there are so many crooks and turns and the trench itself is so narrow that passage along the same is very difficult. To provide for this lateral communication a trench known as the communication or supervision trench is dug. It runs generally parallel to and a short distance in rear of the fire trench and is connected therewith by zigzag approaches. The factor that determines the distance between the fire trench and the communication trench is that it should be at such a distance that a shell bursting in one of the bays would not destroy the communication trench. [Illustration: Plate 23.--Type of communication trench.] The location of the communication trench with respect to the fire trench and the arrangements of the approaches is shown in detail in Plate 1. The profile of the ordinary communication trench is shown in Plate 23. DUGOUTS During the artillery bombardment few men are left in the fire trenches. The remainder of the garrison is held under cover a short distance to the rear. This cover is provided by a system of dugouts connected with the fire trench through underground passageways that lead to the communication trench. This arrangement is shown in Plate 1. A profile of the latest type of dugout is shown in Plate 24. The solid earth cover is from 12 to 18 feet thick, which gives protection from all but the very largest caliber shells. [Illustration: Plate 24.--Type of dugout.] Effective resistance is supplied by roofing materials as follows: 1. From shrapnel bullets: 2-inch planks covered with 12 inches of earth. 2. From 3-inch shells: 4-inch planks supporting 4 feet of earth with a top layer of heavy stones to cause an early shell burst. 3. From howitzers of less than 6 inches caliber: 12-inch beams or logs covered with 8 feet of earth. 4. From the largest caliber guns: 15 to 25 feet of earth. The following table shows the penetration of the German S bullet at a range of 200 yards: _Inches_ Steel plate 3/8 Broken stone 6 Brickwork, cement and mortar 9 Brickwork, lime and mortar 14 Sandbags 24 Sand, loose 30 Hardwood, oak, etc. 38 Earth 50 Soft wood, poplar, etc. 58 Clay 60 Dry turf 80 In addition to the regular "dugouts" for the supports, the latest type trenches have squad dugouts just in rear of the bays of the fire trench. These provide shelter during bombardment for the members of the squad not actually required on duty in the trench bay.