There are many methods of exterminating rats. However, with some methods you may have to deal with dead or injured rats in crawl spaces and gaps in walls. Traditional rat traps may also only be effective for a few uses before having to be discarded. Electric rat traps can be reused many times with minimal wear and tear, even though there are more humane ways of exterminating rats.
Use your saw to cut a base for your trap using the 5 cm x 15 cm (2 x 6 inch) lumber. Ensure that you have enough room for the electric portion of the trap by cutting a part of the lumber that is a minimum of 45 cm (18 inches) long.
Cut a 15 cm x 17.5 cm (6 x 7 inch) piece of copper sheet metal. Use the soldering iron to solder a metal spring to the centre of one end of the copper sheet metal. Turn it over and place it so that the end with the spring attached is at least 2.5 cm (1 inch) away from the end of the base. Attach the other end of the copper sheet to the base using nails. Test the spring end of the copper sheet by pressing down lightly with your finger. It should depress and spring back easily with minimal force.
Take two pieces of insulated electrical wire and strip off about 2.5 cm (1 inch) from one end of each piece. Use the soldering iron to solder the stripped portion to the sheet metal. Extend the rest of the wire out past the base ensuring that you leave plenty of wire hanging off the end for use in later stages.
Set side a brass screw. Strip 2.5 cm (1 inch) of insulation from a long piece of electrical wire and wrap the exposed wire around the head of the brass screw. Lightly hammer the screw with the electrical wire wrapped around its head into the base directly underneath the spring end of the copper sheet. Ensure that what remains of the electrical wire is long enough to reach the transformer.
Make a tunnel to enclose the rat trap. Cut three more pieces of wood the same size as the base and use glue to attach them to the base to make a tunnel. Secure the tunnel using screws. Cut a 15 cm x 25 cm (6 x 10 inch) section of plywood. Cut out a 6 mm (1/4 inch) square and thread the wires through it. Secure it to the back end of the trap -- the side where the wires are.
Wire the transformer to the wires sticking out of the back of the trap. The transformer will help produce enough electricity to kill the rat when it enters the trap.
Bait the trap by placing food at the electric end of it that will be attractive to the rat. Peanut butter works very well. Place the trap in an area where the rats frequently travel. You should be able to tell where because they will leave the highest concentration of droppings in that area. Paint the outside of the trap to match its surroundings if desired. Plug in the power cable of the trap, this will arm it.
A large amount of electricity is required to kill a rat, so it is important to be very careful when constructing and handling an electric rat trap.