Choose any position on undulating ground, form the men in extended order in one line in rear of it, and order them to move up, and mark where each would place his trench in order to fire on an enemy advancing from the front. In doing this it should be an invariable rule that men must lie down, bring the rifle into the firing position, look along the sights, and move forward or back till they see that they have got the best position to sweep the ground in their immediate front (see M.F.E., 31 (3)). Dead ground close to the trench gives the enemy a place in which to collect and organise an assault. Take the men in the same way on to other positions and repeat the lesson till they all understand that the _first thing to be done is this aiming with the rifle to secure a good field of fire_. At first halt them close to what you see is the best line, and afterwards halt them thirty or forty yards from it, and then give the order to choose sites. For instance, halt them on the top of a convex slope and let them find out that the best place to bring fire on to flat ground at its base is somewhere on the enemy’s side of the convexity, for if the trench were made on the top of the slope the ground immediately in front would be hidden by the convexity. The section commanders must help the men in choosing sites. After the men have fixed and marked the proposed sites, let them lay down their rifles three paces in rear and kneel or lie down at the rear edge of the site as if waiting to commence work while you and section and platoon commanders go round and examine the line. Ask details from the men—how high they would make the parapet, how thick it should be, how they would make head-cover, how they would conceal the work, and so on. _Traverses and broken lines of Trenches._ Repeat the exercise as above, but this time have the men in sections or small groups, and the trenches made not in one line, but in short lengths, separated by traverses. You will have to explain the construction and use of these to prevent enfilade fire (if not from long range), and to localise shell bursts. Again, have lines of trenches mapped out in short lengths on an irregular front, some a little forward, some a little back, with the earth at each end, banked up on the flanks with the same object (M.F.E., 33). _Short Trenches for Two Men._