_Cover for Guns._--Some degree of cover for guns, in addition to the shield, is always desirable. If the gun stands on the natural surface of the ground, the cover is called an epaulment. In that case a bank is thrown up in front of the gun, about 1 ft. high in the centre, and 3 ft. 6 in. high at the ends. On either side of the gun and close up to the bank is a small pit for the gunners. The rest of the earth for the epaulment is got from a trench in front. If the gun is sunk, the shelter is called a gun-pit. In this case there is no bank immediately in front of the gun. Shelter can be got more quickly with a pit than an epaulment, but it is generally undesirable to break the surface of the ground. Obstacles. The commonest forms of _obstacle_ now used are _abatis_ and _wire entanglements_. Fig. 93 shows a well-finished type of abatis. The branches are stripped and pointed, and the butts are buried and pegged firmly down. Wire entanglement may be added to this with advantage. An abatis should be protected from artillery fire, which is sometimes done by placing it in a shallow excavation with the earth thrown up in front of it. [Illustration: From _Mil. Engineering: Field Defences_, by permission of the Controller H.M. Stationery Office. FIG. 93.--Abatis.] Wire may be used as a _high_ or _low entanglement_ or as a fence or trip wire or concealed obstacle. The usual form of high wire entanglement consists of several rows of stout stakes 4 or 5 ft. long, driven firmly into the ground about 6 ft. apart, and connected horizontally and diagonally with barbed wire. [Illustration: FIG. 94.--Crows' Feet.] [Illustration: FIG. 95.--Plan and section of Trous-de-loup.] _Palisades_ are still used, and need no description. They were formerly often made bullet-proof, but this is no longer possible. _Fraises_ are seldom heard of now, though they may appear occasionally in a modified form. They were much used in connexion with deep ditches, and are palisades placed so as to project horizontally from the escarp, or sloping forward in the bottom of the ditch. _Military pits_ both _deep_ and _shallow_ (the latter, shown in fig. 95, called _trous de loup_) are not so much used as formerly, because the obstacle is hardly worth the labour expended on it. Both, however, were employed in the Russo-Japanese War. _Crows' feet_, formerly much used as a defence against cavalry, are practically obsolete. They consisted of four iron spikes joined together at their bases in such a manner that however they were thrown down one point would always be pointing upwards (fig. 94). _Chevaux-de-frise_ (q.v.) were formerly a much-used type of obstacle.