A design, known as the “T” shaped fire-trench, makes an adaptable basis for entrenching under these conditions. Many lengths of a continuous traversed trench have no great field of fire, and yet, having been dug, they must be held, and unless properly held and kept in repair, they naturally become a source of danger. As shown in the sketch, a traversed trench consists of a series of fire-bays interrupted by a series of traverses. The object of these being to localize the effect of shells or bombs landing in a fire-bay, and preventing enfilade fire down the length of the trench, as well as localizing any entry of the enemy into your line. Dimensions vary up and down the line. Sometimes according to the lay of the land, sometimes according to the opinions, whims or fancies of the regiments making them, but the following dimensions should be kept in mind, and it will be found that they show the average of the whole general line on the Western Front. Fire-bays generally are from 12 to 18 feet long (defendable by 4 to 6 men, but accommodating 8 to 12, when necessary) plus a 2-ft. covered sentry box recessed into the traverse and giving room for one more man; this depending entirely on the energy and initiative of the men occupying the section. Every traverse averages 9´ x 9´ which includes a fairly liberal allowance for wear and tear, and is the minimum allowance for stopping enfilade fire and localizing fire. As the width from front to rear varies, depending on the amount of shell fire, it should be wide enough to allow a certain amount of lateral traffic without interfering with those who may be firing. Three feet may be taken as the maximum width at the bottom of the trench, that is, 1½´ for traffic and 1½´ for those firing, with a slope to the sides of from 10 to 15 degrees from perpendicular, thus lessening the tendency of the walls, whether revetted or otherwise, to slide in. The depth of the trenches varies also, for the same reasons that cause the width to vary. Recesses should also be dug at various and favorable places for the storing of ammunition and bombs.