These things came in several variations. I have one that is quite nice but have only used it once. This is solid tire mounting device. I say solid tire but really the tire was hard rubber with a 3/16 core hole to accept a steel wire for mounting. The rims are usually pretty deep cut and you run an 1/8 inch steel wire through the core of the tire. You then wrap the tire with wire around the rim. You use just enough rubber to fit the rim plus about a quarter inch over. You use about a two foot longer length of wire coming out of each side. This tool facilitates three actions. It spreads the rubber tire apart while holding it on the rim all the while holding the wire and allowing you to bind the tire to the rim.
As you turn the crank the wire is pulled tighter and tighter and keeps the ends parallel to each other but going in opposite directions. Think of it like the first step in tying a square knot. After the wire achieves the proper tension you get out your brazing material and torch. You braze the ends parallel to each other for about an inch and cut the excess wire away. Most folks I have seen do this use a metal shield under the wire to protect the rim. Remember the rubber is still pulled back away from the heat by the tool. After you cut the excess away you get out your file and smooth the brazed area and especially the cut ends. When nice and smooth you remove the tool and the rubber recovers over the brazed wires and leaves a small seam.
I have done this myself just once for my bike and it is a trip. No way you can do an on the road fix. I had a brazed wire break during a ride on my high wheel and luckily it was the rear wheel. It just rolled off the rim and I was able to abandon the bike before anything serious happened. A similar failure of the front tire has sent many a wheelman to the hospital.
Here are photos of two different models.
Ray Homiski
Elizabeth, NJ