Twisted wire is simply two regular wires twisted together. Having two wires so close together causes the signals coming out of each wire to cancel each other out and creates a dead-zone where the dog can walk over safely without getting the warning or the correction. But, the twisted wire can only be used in certain situations. The main use for twisted wire is to connect the main boundary loop to the control box. You can also use the twisted wire to connect one loop to another loop. But, you absolutely cannot use the twisted wire as part of the main loop. The video below shows you how to use twisted wire and how you can make your own.
Imagine you had a boundary going around your entire property, with the base station inside your home. You have everything connected and test to make sure everything works fine, but the layout is not ideal.
Cut the boundary wire where it turns in from the perimeter toward the house and disconnect the wire from the control box. (If you bought the pre-twisted you would replace this section with the pre-twisted wire, so skip straight to step 5 where we connect up the twisted wire.) The rest of us will need to twist the wire ourselves.
Now we splice the twisted wire back into the boundary loop on one side, and re-connect the twisted wire to the control box on the other side.
You would have two strands of wire coming into the base station from the perimeter. This would be inconvenient because the dog could not cross the section of the wire.
Twist the two wires together, so that there is about one twist per inch. Err toward having more twists rather than less. The easiest way to twist the wires is to attach them to an electric drill and let the drill do the twisting for you.
Voila! Your dog can now safely cross over the twisted section without hearing the warning beep or getting the correction.