My Dad had one of these. He used it to heat up solder in a little cup made of what looked like 1 inch or 3/4 inch pipe. The cup had a steel handle with wood over the steel to insulate you from the heat. The cup was filled with solder. When joining two wires you twist them together then dip them in the molten solder. It was a good idea to keep some rosin to dip the wire in before you dipped it into the molten solder. The heat from the solder in the cup made the joint very smooth and strong. The blow torch was kept in a central area away from flammables and the solder cup heated periodically as you were joining wires. This was before the twist on connectors we use today were common. The joint was allowed to cool then wrapped securely in electrical tape to prevent any chance of shorting. I imagine the joints were a lot stronger and less prone to thermal loosening than todays twist on connectors. It did require vigilance to make sure the torch was always pointed in a safe direction.
And do I make joints like that now a days? Nope, I use the twist on connectors. If for some reason I am asking a wire to perform close to its specs I might twist the leads, solder them with a soldering gun, then put a twist cap on. That is fairly rare though.