Snipers were equally ingenious in concealing themselves. They frequently used rifles which were connected with a dummy butt and had a periscope sighting-attachment. This attachment was called a "sniperscope." The rifle-barrel could be pushed through a loophole in the parapet and the sniper standing safely below the parapet could hold the dummy butt to his shoulder and aim his rifle with perfect accuracy by means of the periscope. It was next to impossible to locate a sniper hidden in this way. One method of doing it was to examine rubbish, tin cans, or any object that had been penetrated by a bullet and note the direction taken by the bullet. This would give a line leading toward the source of the shot, and when a number of such lines were traced, they would cross at a spot where the sniper or his gun was stationed, and a few shell would put the man out of business. Dummy heads of papier mâché were sometimes stuck above the parapet to draw the fire of enemy snipers and the bullet-holes which quickly appeared in them were studied to discover the location of the snipers. [Illustration: Redrawn from Military Map Reading by permission of E. C. McKay FIG. 2. A fixed rifle stand arranged to be fired after dark] Sometimes fixed rifles were used. These were set on stands so that they could be very accurately trained upon some important enemy post. Then they could be fired in the dark, without aiming, to disturb night operations of the enemy. Often a brace of rifles, as many as six, would be coupled up to be fired simultaneously, and by operating a single lever each gun would throw out the empty cartridge shell and bring a fresh one into position. STEEL BRIER PATCHES The most important defense of a trench system consisted in the barbed wire entanglements placed before it. Barbed wire, by the way, is an American invention, but it was originally intended for the very peaceful purpose for keeping cattle within bounds. Long ago it was used in war, but never to the extent to which it was employed in this world struggle. The entanglements were usually set up at night and were merely fences consisting of stout posts driven into the ground and strung with barbed wire running in all directions, so as to make an impenetrable tangle. Where it was possible to prepare the entanglements without disturbance and the position was an important one, the mass of barbed wire often extended for a hundred yards or more in depth. Just beyond the entanglements trip-wires were sometimes used. A trip-wire was a slack wire which was laid on the ground. Before being laid, the wire was tightly coiled so that it would not lie flat, but would catch the feet of raiders and trip them up. Each side had "gates" in the line through which this wire could quickly be removed to let its own raiding-parties through. Sometimes raiders used tunnels, with outlets beyond the barbed wire, but they had to cut their way through the metal brier patches of their opponents.