It is only under very exceptional circumstances that under-cutting a trench wall is allowed, and then the shelter should be cut in the rear wall only. These shelters must be carefully supervised and watched by the officer, as men are very often careless, with the result that the shelters are dug in a hurry and poorly. Then it rains, the shelter falls in, and the men are no more. It should be high enough for a man to sit up straight, and long enough for him to lie down in, and deep enough for two men to lie side by side. It should be raised at least a foot above the floor level in the trench to prevent water from the trench floor coming in. A shelter smaller than these dimensions is useless. It has a demoralizing effect, destroying all activity, mental and physical. These shelters can only be properly made by cutting into the rear trench wall the necessary depth and length and right to the top. Then, with any material which is convenient, such as corrugated iron, brushwood, old rubber sheets, revet the sides and back. A corrugated iron roof is supported on posts at a depth of about a foot to a foot and a half below the normal level of the ground. Then, when possible, cover this with rubber sheets. If not possible to procure rubber sheets, simply cover with dirt excavated from shelter, taking care that it does not rise higher than your parados.

A fire-trench, however, is not a proper place for shelters, and they are generally better as a weather protection than a shell-proof shelter. Even this should not be favored too much, as it tends to cause obstruction, delay and inconvenience in the passing of troops. The real dugouts for the accommodation of men holding a line are generally behind the fire-trenches in an immediate support line, or as in the case of T-bays, in the control trench and communication trenches leading to and from them. These are large dugouts, having a depth of 30 and 40 feet, and in some cases capable of holding 100 to 250 men, generally having from 5 to 10 exits and entrances. Here the men stay during bombardments and are generally safe from any caliber shell which may light on top, unless a half dozen should light in the same particular spot.

This work is generally of a very skilled and technical kind. Plans, drawings and labor are supervised by the engineers, expert tunnelers being used in constructing work, although the infantry supplies working parties to dispose of the dirt, etc., resulting from these excavations and to carry the materials and tools needed and required in the construction.

The design and general scheme of a small dugout which can be made by the infantry under the supervision of an officer, without the aid of an engineer, are here given. The dugout should be approximately 6 feet from floor to roof and about 8 feet wide, with an approximate length of 12 feet, thus allowing men to lie down and yet leave room for passage through. The width depends upon the number you intend to have occupy it. Each man requires 18. Depth to be dug below ground depends entirely to what extent you may raise the roof upon the ground without making an unduly exposed hump which will at once tell the enemy a dugout is there. The thickness of the roof should be approximately 6 feet, constructed with side posts, cross beams, corrugated iron, waterproof oilcloth, sandbags and soil. Sandbag revetments should be used in the strengthening of side posts. When possible, although hardly ever so, walls should be lined with waterproof oilcloth and entrances so placed that they get as much sun as possible.

Great care and attention must be given to these dugouts, and even though taking a little longer than seems necessary, care must be taken to see that they are substantially constructed, otherwise they are in a constant source of danger of cave-ins during heavy shelling and bad weather. Not more than 10 men should occupy one of these dugouts. Then, if accidents happen, your casualties are not so great.

The roof of these dugouts should be prepared in a manner tending to withstand as high shell shock as possible, and for this purpose the following table would be of some use, any part of which, or a combination of all, will give some idea of what is required.