Originally Posted by
Jim Becker
I agree that in most cases, two cleats aren't really necessary to support things to be hung. Where I might employ top and bottom might be for, say, hanging a cabinet that will house things like portable electric hand tools, such as routers and the like. It's nice having that option and that's a good reason to keep the spacing of cleat rows "standardized" in the shop so you can easily move any "double cleat" items elsewhere down the road.
My kitchen cabinets are hung with double french cleats.
You would be stunned at how heavy a cabinet full of dishes is.
I personally would not use solid wood, unless it was from some very specific species of wood, for french cleats. Birch ply, or scrap cabinet ply, make very strong cleats.
"The first thing you need to know, will likely be the last thing you learn." (Unknown)