(_e_) Probability of being knocked out of hand. (_f_) Weight, length, shape of blade. (_g_) Shape of handle. It was found that the model 1917, although a satisfactory knife, could be improved. Therefore the trench knife known as Mark I was developed partially by the American Expeditionary Forces and partially by the Engineering Division of Ordnance. This knife was entirely different from the model 1917, having a flat blade, metal scabbard, and a cast-bronze handle. It was a combination of all the good points of all the knives used by the foreign armies. The Government placed orders for 1,232,780 of the new knives. Deliveries were to have begun in December, but before that time peace had come and the orders had been reduced to 119,424. The new model knives were to have been manufactured by A. A. Simons & Son, Dayton, Ohio; Henry Disston & Son, Philadelphia; Landers, Frary & Clark, and the Oneida Community (Ltd.). All contracts were canceled except the one with Landers, Frary & Clark. [Illustration: 1917 MODEL OF TRENCH KNIFE AND SCABBARD.] [Illustration: MARK I TRENCH KNIFE WITH FLAT BLADE, DESIGNED BY A. E. F.] [Illustration: WIRE CUTTER (ONE HAND).] [Illustration: FRENCH WIRE CUTTERS.] [Illustration: WIRE CUTTER, MODEL 1918, SHOWING SPECIAL RUBBER HANDLES. TESTED AT 10,000 VOLTS.] PERISCOPES, BELTS, ETC. Another new article in the equipment of our soldiers was the trench periscope, a device enabling a man to look over the edge of the trench without exposing himself to fire. The ordinary periscope was merely a wooden box 2 inches square and 15 inches long, with an inclined mirror set at each end. Production was commenced in October, 1917, by two companies, and 81,000 were delivered by the middle of January. In August, 1918, an additional lot of 60,000 was ordered, but the deliveries of these were slow. An even simpler periscope was merely a mirror about three inches long and an inch and a half wide which could be placed on a bayonet or a stick and set up over the trench so that it gave a view of the ground in front. A total of 100,000 of these was delivered before the end of July, 1918, and 50,000 additional ones before November. Further facts about periscopes are set down in the chapter in this report relating to sights and fire-control apparatus.