The utmost quiet should be observed, and there should be no cooking or smoking. The intervals between outguards will depend upon the situation and the terrain. The line of observation is not necessarily continuous, but all avenues of approach must be carefully guarded. The distance of the outguard from the support likewise is governed by the terrain, but in general may be said to be from 300 to 400 yards. In thick country or at night outguards patrol along the line of observation between posts. Communication between outguards and the support is by signal and messenger, in special cases by wire. Members of the outguard retain possession of their weapons and do not remove their equipment. Sentinels from the outguard are posted so as to avoid observation, but so that they may have a clear lookout and be able to see, if possible, by day, the sentinels of the adjacent outguards. Double sentinels are always posted near enough to each other to communicate easily in ordinary voice. Sentinels are generally on post two hours out of six. For every sentinel and every patrol there should be three reliefs, and outguards should be of a strength sufficient to allow this. The position of a sentinel should be selected with reference to observation. It may be advantageous to place a sentinel in a tree. Sentinels furnished by cossack posts or sentry squads are kept near their group. Those furnished by their pickets may be kept as far as 100 yards away. Reliefs, visiting patrols, and inspecting officers approach sentinels from the rear.