Smaller leashes in the same style, but made of less stout leather, can very well be used for the smaller hawks, and usually are so. But when these hawks are doing a great deal of flying, as they should, and doing it twice a day, the trouble of constantly unfastening the ring-swivel from the jesses and fastening it on again becomes very tiresome, and even vexatious; and it is a common practice to use spring-swivels permanently. The outer ring of these (unless they are made specially) is too small to admit the passage of a flat leash; and it will be found more convenient to use thongs shaped like a porpoise-hide boot-lace. In fact a long leather boot-lace makes about as good a leash as can be wished for. The function of the button is fulfilled by a simple knot tied in the end of the lace. Or in order to save still more time, the lace may be permanently attached to the spring-swivel in the manner shown in the diagram (Fig. 25). By making the knot an inch or two away from the ring of the swivel, instead of close up to it, enough length of tether is left, when the leash is tied round the pole, to enable a merlin or sparrow-hawk in short "racing jesses" to shift about a bit on the perch. The proper place for a hawk, when not out of doors, is the screen-perch (Fig. 23). The bar on which the hawk stands may run from wall to wall of the hawk-house, or, if this is not convenient, it may be supported on arms or brackets reaching out from the wall to a distance of not less than 30 in. for a big hawk, or 2 ft. for a little one. Where this arrangement is also impossible the bar may be supported at each end on a post or tressels so securely fastened or weighted that they cannot be upset or moved out of place. Round the bar, which should be of wood, is wrapped a padding of baize or other soft stuff, and over it a covering of canvas stretched very tight. The canvas may be nailed to the pole, or stitched together, on the under side. A screen, or curtain, of canvas must be attached to the under side of the perch, and hang down from it for more than two feet, to form a sort of ladder, by which any hawk may climb up again as often as she bates off and hangs by her leash and swivel. The ends of this screen may be kept down with weights attached to it, or stretched by a sort of guy ropes from the lower corners, so as to keep the whole flat and taut. In perches for small hawks, the same canvas which is rolled round the pole is often allowed to hang down and form the screen. In this case slits or holes are made in the canvas just below the pole, through which the leashes may be passed when fastening the hawks to the perch. A space of at least 2 ft. should be left between each big hawk and that which stands next her on the perch; and 18 in. between each of the small ones; and there should be rather more space between the end hawk and the wall or the bracket of the perch, whichever it is.