This subject is too vast for more than a mere outline in these pages. The kite-shaped, round, and triangular shield appears in the twelfth century. The two first-named are long, and either bowed or flat. They were held over the breast by a strap going round the nape of the neck, called a “guige.” Shields of the thirteenth century were either small and “heater” shaped, or larger and rounded. Pavises were very large shields to be placed before the bowmen as a defence, and were provided with an inner prop to hold them upright on the ground. As to ordinary shields, most of the thirteenth century forms extended into the fourteenth, when the bouche, or hole cut in the right corner as a spear-rest, was introduced. They were pear-shaped, triangular, heart-shaped, circular, oval, curved, and sometimes nearly square. The round buckler was carried in the hand, while the larger shield was borne on the arm. The material was generally of wood or leather, or both combined--the latter often embossed. They were more or less fortified or bossed, and sometimes partly or wholly of iron. For tyros, basket-work was used. Shields generally bore a heraldic device, or other cognizance, and were frequently curved, bossed, and spiked. The usual shield of a knight of the fifteenth century had the bouche, was convex, and about two and a half feet long by about a third of that broad, and pointed at the bottom. In the sixteenth century ordinary shields were seldom used, but an immense amount of fine artistic work was lavished on the pageant shields of that period, an example of which is given in Fig. 15. The tournament shield is described under the heading devoted to these games. [Illustration: Fig. 15.--Pageant Shield, formerly in the collection of Prince Carl of Prussia.] CALTROP, OR CROW’S FOOT. This, the Roman murex or tribulus, was a sharp point of iron standing upright, fashioned like a crow’s foot. They were strewn broadcast on the ground, for the purpose of maiming horses in a charge of cavalry, or placed on a moat filled up with fascines, or on a breach to resist an attempt at escalade. Knightly spurs have been known to have been used for this purpose. The name is an abbreviation for cheval-trap. There are some specimens in the Rotunda, Woolwich, varying in height from 1.25 to 2.5 inches.[30] SPURS.