Explanation of Letter Symbols (_a_)-(_b_) The road on which the Blue regiment is marching. In military orders and problems roads are designated by naming places located on them. For example, the Longs-Emmitsburg-Fairplay road would mean the main road passing through these places. When military maps are made all cross-roads and road-forks should be numbered and all hills and other prominent topographical features either designated by their local names or given letter designations. This will greatly facilitate their designation in orders and messages. When maps have grid lines on them the location of points may be designated by the use of coordinates. (_c_) Some point, a number of miles distant, in the direction in which the troops are marching. (_d_) The point on the main road where the support of the advance guard of the column has arrived. It should be about abreast of (_f_), (see below). (_e_) The designation of the flank guard, right or left. (_f_) The point at which the flank guard is supposed to have arrived. The point where the Terrain Exercise is to begin. (_g_)-(_h_) The road on which it is intended that the flank guard is to march and along which the Terrain Exercise is to be conducted. This road should lie approximately parallel to and not more than a mile distant from the road on which the main body is marching. If no such network of roads exist, the Director may explain to the class the conditions and assume that the nearest road is about a mile distant and work out the problem on that assumption. This procedure strains the situation a little and robs it of some of its reality. The members of the class will have to make the best of it and will have to draw upon their imagination to picture it. (_i_) A locality some miles distant in the direction of which the Blue force is marching. (_j_) Localities or places some distance to the flank of the Blue force and in the direction of the road on which the flank guard is marching. Procedure The members of the class are conducted to (_f_) where the Terrain Exercise is to begin. The Director distributes the sheets containing the Special Situation Blue and the Situation No. 1. A few minutes are allowed the members of the class to look them over. The Director then reads the problem aloud, the members of the class following from the copy in their possession, and makes such explanation as may be necessary. One or more members of the class are called upon to state their understanding of the tactical situation. Explanation _The Director_: “Before going ahead with this exercise I want to make a few remarks about a flank guard.