Electronic Circuits and Projects Forum

I am incorporating two 12 v LED light strings into a mirror frame for my bathroom powered by a DC transformer. One string points up, and one down. I purchased a mini toggle on-on-on switch for it that I would be able to turn the down lights on, or the up lights on, or both. As I started to wire it up, I realized that I would backfeed from my middle circuit making the switch useless as both strings would be on all the time. How do I prevent the backfeed on these two light strings, with a Diode? I found this on-line: 1N5818, 1A, 30V Schottky Diodes, would this work, and how should it be wired in? Thanks for your help.