When the front wall of a trench is to be revetted and only sandbags are available, the wall should first be cut to a slope of from 10 to 15 degrees from the perpendicular, and the loose soil obtained, if dry, placed in the sandbags. When there is an unrevetted fire platform, this should be also cut away and put, if dry, in the sand bags. A bed should then be dug about 6 inches into the solid bottom of the trench (disregarding the soft mud which for foundation purposes is of no use) and sloping down into the parapet at right angles to the slope of the front wall. Into this bed place a row of headers. On this row place a double row of stretchers. Joints must always be the same manner as brick-laying; that is, care taken that the joint where the ends of the stretchers meet does not come immediately over the joint between the headers and the lower row. Sand bags should now be beaten down flat, generally with a wooden mallet provided for this purpose; then alternate rows of headers and stretchers laid; each layer being flattened out with the mallet until the top of the parapet is reached. The top layer should always come out as headers. [Illustration: Headers, Stretchers, Headers] Twenty-five headers or twelve stretchers, or sixteen mixed, is the average required for revetting every superficial yard of trench. The slope of a front trench wall, even when from 10 to 15 degrees from perpendicular, is apt gradually to assume the perpendicular, and then fall in, owing to the sinking of the trench bottom or the actual thrust of the earth in front. This can, however, be checked by using 6´ to 8´ stakes driven well into the front wall foundation, and at the same angle as the front wall. Then, wiring the head of these stakes to what is known as an anchor-stake driven about 10´ into the ground in front of the trench. Sandbags come in bales of 250, which are again divided into bundles of 50 each. On a carrying party it is an average rule that each man carry 100 sand bags.