The final assault. The introduction of modern breech-loading rifled guns, howitzers and mortars, rapid-fire and machine guns, and magazine small arms has brought with it the need of a higher grade of mechanical skill and improved machinery for making the ordinary repairs. This imposes upon both attack and defence the necessity for providing machine shops and tools fitted for work of this kind, with the steam power required to drive them. In connection with these, steam sawmills and other simple wood-working machines should be provided, as well as all other available labor-saving appliances which can be used to lighten the labor of the troops. Portable tools, such as picks, shovels, crowbars, rammers, axes, hatchets, bill-hooks, gabion-knives, hammers, saws, carpenters', joiners' and blacksmiths' tools, etc., etc., must be provided. =10.= The principal =special tools and appliances= used are the following, viz.: sap-forks, sand-bag forks, scrapers, sap-shields, measuring-rods of various lengths, pocket compasses with attachments for fastening them to measuring-rods, tracing-lanterns, dark and ordinary lanterns, tracing tape or cord, tracing pickets or stakes, fascines, gabions, hurdles, sand-bags, blindage and gallery frames and sheeting, etc., etc. The _sap-fork_ and _sand-bag fork_ (Pl. I, Figs. 1 and 2), about 4½ and 4 feet long, respectively, have steel heads with three and four prongs, as shown in the figures, those of the sap-fork being sharp and those of the sand-bag fork blunt. They are used for handling and placing gabions, fascines, and sand-bags in position when, without their use, the sappers' arms would be exposed to fire. The _scraper_ (Pl. I, Fig. 3) is a large hoe, of about the dimensions given in the figure, used for levelling off the surface of parapets, etc. The _sap-shield_, introduced by the English (Pl. I, Figs. 4 and 6), is a flat plate of mild steel 3 feet 6 inches by 1 foot 9 inches × ¼ inch, with two handles on its back as shown. Total weight, about 80 lbs. It may be used as shown in the figure, and sometimes by small parties as a body-shield in such operations as blowing in gates, etc., etc. _Measuring-rods_ of rectangular cross-section, straight and divided into feet and inches, are needed for special purposes; but the ordinary rods are cut from round brush wood and to the length required. _Tracing-tape_ is usually a white tape, about 1½ inches wide, in lengths of 150 feet, marked at equal intervals, usually 5 feet, by short pieces of tape sewed to it. A loop of strong cord is fastened to each end. For convenience in use it is ordinarily rolled into a ball. _Tracing-pickets_ are about 18 inches long and one inch in diameter. To make them visible in a dim light the bark is removed from them. _Ordinary pickets_ are usually 3½ or 4 feet long, 1½ to 1¾ inches in diameter, sharpened to a triangular point.