All the walls of the traverses must also be revetted, generally with the sandbags and in exactly the same manner as the front walls of a fire-bay, care being taken to keep it well sloped. This leads to a lessening of protection afforded the occupants by making a greater width at the top of the trench, but it is absolutely necessary unless you wish your whole traverse to gradually fall in, when you are in a position of having no protection at all. The top of the traverse may be and is often several feet higher than the parapet, if the fire-bay it protects is exposed to enfilade fire from the enemy trench at a higher level. But when this is not the case, the traverse should not be higher than the parapet or parados, and should slope down towards the enemy to give the appearance of being merely a continuation of the parapet. The traverse should never be less than 9´ wide, allowing 2´ for a sentry box, although this sentry box is no longer generally in use. What are known as overhead traverses are made generally in a communication trench leading up to the front line, and which in certain parts the enemy are able to look into. These overhead traverses give to this particular place the protection which is necessary. They are quickly and easily made by placing corrugated iron, logs or strong branches, or floor boards, across the top of the trench and putting sand bags on the top of these. When the trench walls are weak, or even on general principles, the sides supporting this overhead traverse should be revetted with sandbags. The sentry boxes, although not in general use now, are described, more for general information than anything else. They are dug or recessed in the traverse at either end of the fire-bay and must have an observation slit in the parapet for use by day, but no loophole facing the enemy, as regardless of the care and caution used in the construction of these loopholes, they will sooner or later, generally sooner, be observed by the enemy and the sentry box made useless. During an attack this sentry box is never used, except for stores or the placing of wounded, as there will always be plenty of room for the late occupant in the fire-bay itself. Sometimes, when energy and time permit, an enfilade fire loophole is made through the traverse and facing the next fire-bay, but this has as much value for making easy verbal communication from one fire-bay to another as it has to the checking of attacking forces. LISTENING POSTS