Coop Nest Box Lid Repair

[Mother of Chaos]

Roof and its fasteners will expand and contract over time in weather like everything does, and may not be a 100% water tight seal despite rubber grommets. Placing fasteners on top of the ridges keeps it out of the path of water. If they sit in the channel where the water flows, the screw heads create mini dams/blockages that hold water (and debris collection that holds even more water), and thus promotes leaks that can be avoided by fastener placement on installation. Hope this makes sense

I knew that attaching through the tops was the proper way to do it, but I never knew why! Thanks for the explanation.