you slide the connector over one of the wires, intermingle the two wires and slide it back. When you heat it, solder melts in the center ring creating a join in the wires (no soldering gun required). The heat shrink tubing is a higher heat type and shrinks around the wires sealing it from moisture. Done. I watched the video and realized I didn't have to solder the wires first as the ring has solder inside it. (there were no directions in the package)

I can see where in some circumstances heat might melt the solder but if that happens you would already have had a bad splice and resistance.

video http://www.youtube.com/watch?v=d83XuNDnHLI&feature=related