The sap-shield is designed to be used in special cases for covering the head of a full sap (described further on), in which case it is placed as shown on Pl. I, Fig. 4; and also as a body cover for a man moving for a short distance in the face of a heavy fire, as is necessary at times in sapping and mining operations. It has not yet stood the test of service in a siege. SPLINTER-PROOF COVER. =20.= =Splinter-proofs= for the guards of the trenches, for field-hospitals, latrines, etc., should be provided as soon as possible after the parallels are finished. They may be placed in the returns of the approaches, or in rear of the parallels, and be connected with them by trenches. Pl. II, Figs. 14-16, show their construction when in rear of the parallel and revetted with logs, fascines, or sawn lumber. The trench is 9 feet wide by 4½ feet deep. Its front edge should be 25 or 30 feet in rear of the reverse slope of the parallel. This width of trench will allow 2 to 4 men per yard of its length to work advantageously. They should finish it in 8 hours. In digging the trench the earth is thrown out on both sides, leaving a berm of about 1½ feet on each side to allow the woodwork to be properly placed. When this is completed the earth in rear is thrown forward to complete the cover, as shown in the plate. Steps for egress and openings for light and ventilation may be placed at intervals along the rear, and, when desirable, bunks may be built, as shown in the figures. When the splinter-proofs are built in the returns of the approaches, the overhead cover may extend entirely across, steps and openings being provided as in the previous case; or posts and longitudinal beams may be set in the trench to hold up the rear end of the cross-beams, leaving the rear of the splinter-proof open. Portions of this may be closed, if desired, by leaning short posts or fascines against the longitudinal beam and banking earth against them. The splinter-proofs may generally be drained into the parallels or approaches. When this cannot be done drainage-pits must be used. Limited portions of the splinter-proofs may be protected against leakage through the earth cover by first filling over the covering beams with earth, packing it to a smooth surface with a gentle slope, placing upon it raw hides, roofing felt or other waterproof material, and then completing the cover by adding the necessary thickness of earth, giving finally to its top surface a slope to carry off the rain. BOMB-PROOFS.