I was in the dollar store last week and they had solar stake lights for a buck. I bought a bunch as they are a cheap source of solar cells, diodes, and LED's. I pulled the head out of the stake and checked it against a couple hole saws I had, looked about 1 1/4 inches. A quick check in a piece of scrap plywood verified it. I drilled three holes in the south(ish) wall of my coop and shoved the lights in the holes. In the future I will caulk them in. They aren't bright, but give off enough light to check on the girls at night and do any quick simple tasks. They don't last all night, but are still on when I go to bed after getting home from work at midnight. When they quit working I can probably get new ones or replace the batteries (i can get to them by removing a couple screws), but batteries would cost more than the lights! Simple, cheap and effective!