When putting several pieces of the yard long rail together, it is better not to actually solder or braze the lengths together but rather just provide electrical connections between the rails with loops of wire. The reason for this is that the layout expands and contracts a lot over the years and having a solid piece of rail many yards long will make for difficulties with kinking and so forth of the track. Better to allow the rails to move about a bit and that will allow the track to stay where it belongs. If you're laying your own rail, butt soldering with silver (5% or so silver) solder will do fairly well in place although working a piece of metal under the rail for additional support will help.
-- Why isn't there an Ozone Hole at the NORTH Pole?