If rubber hydraulic hose is used, slit it open straight along one edge. Clip the slit open hose around the perimeter of the shield. This kind of edging is held in place with short lengths of leather. These must be long enough to go tightly aground the hose and still have enough overlap to allow a round head stove bolt with two washers to be tightened through the leather and the shield. Check the dumpsters at your local bicycle repair shop.
Reasons are mostly cost.
Cut the tire so that the circle is broken. Trim away approximately 4 to 5 inches of sidewall from both sides of one end, leaving a strip of 4 or 5 inches of tire thread on that end. On round shields overlap the thread strip and a square cut end at the rear or elbow point of the round. On a heater shape, the joins are at the rear top angle and at the point of the heater. Be advised that heater shapes usually require two 10 speed tires.