There are two methods. One is through a hinged tube with the wires inside attached to the door post and into the door, the other is with contacts on the door jamb and door posts. I prefer the tube method. Numerous companies selling them. I always see them advertised in Street Rodder and other magazines. Bought the last set I got off eBay....now if I could find the invoice I'd let you know the company..... If I find it, I'll post it....Not exactly the world's best filing system around here... My secretary quit----about 18 years ago....