I use one similar on my planes that are cowled. One wire is grounded to the engine and the other to the backside of the glow plug extension. These are nice if you are using a glow ;panel where you have the wire going to the glow plug. Keeps it out of the way. On my sea planes I have it mounted on the top.. BTW CG. poached egg, bacon not crisp-hash browns crispy and Chock-full-of-nuts coffee. What a way to start the morning.