The front wall of the trench is called the parapet, and the rear wall, the parados. Above the trenches, on the intervening ground, is overland. In the bottom of the trenches, when the water has not washed them away, are trench mats, or small, rough board walks. Sometimes the mud or sand walls of the trench are supported by revetments of wire or wood. No Man's Land is the area between the firing lines of the opponents. It is a barren area of shellholes, barbed wire, and desolation, and may be from forty yards to 300 or more yards wide. Commonly, on standing fronts its width is about one hundred yards. Saps are trenches extending out into No Man's Land, and used for observation purposes or for listening posts. They may end in craters, or large cavities in the ground, made by the explosion of mines. Dugouts are cavities off from the trenches, connecting with them by narrow passages. The dugout proper is a cavity, small or large, used for living in and for protection from shell fire. They may be superficial, having only two or three feet of sandbags--more properly, bags of sand--for a roof; or they may have a roof ten to forty feet in thickness. But the term is often used carelessly for any kind of shelter at the front. At dusk and dawn the men usually "stand to," that is they stand, rifle in hand, in the trenches ready to repel any attack of the enemy. During the dark hours the men take part in working parties, or fatigues, to bring in water, clean the mud from the trenches, carry rations or ammunition, and dig holes or dumps in which munitions, flares, or equipment are stored. Fatigues are rather disliked by the men, for they are laborious and just as dangerous as other work in the lines. In speaking to each other, and often in official communications, abbreviations are much employed among officers and men. For example: O.C., or C.O., is used to signify the officer commanding any unit, whether it be the Lieutenant Colonel in charge of a battalion, or the Major, Captain, or Lieutenant in command of a company; the M.O., or the Doc., is commonly the shortened form for the Medical Officer; and H.Q. signifies headquarters, and may apply to company, battalion, brigade, divisional, corps, or army headquarters, any of which would, generally speaking, be specified, unless the conversation or communication made it plain which was meant. After big advances there are varying periods during which trench life is more or less abandoned for open warfare. After an advance the consolidation of the land taken consists of again digging trenches and dugouts, preparing machine-gun emplacements, bringing up the artillery, and establishing communications. During this transitory period the losses are often heavy, because of the poor protection afforded the men and the fact that the enemy is well acquainted with the ground which he has abandoned, willingly or unwillingly. CHAPTER II OVER THE TOP