Radio Shack once again saved the day .... The sign out front says "3 Days and we're gone ... everything must go ... office shelves, cabinets, furniture must go" .... So what do I go in there to buy? .... A Reed Relay for $1 that I was going to take apart anyway.... I just needed the Reed switch to make an electronic float sensor for a bilge sump pump. ... What's a Reed Switch in case you asked? Literally two thin pieces of metal (Reeds) that are separated by a millimeter or so in an insulated glass capsule. When a magnet is in their presence they become attracted to one another making an electrical connection. Placing a magnet on a water float creates an electrical means for detecting the water level.