The French Cleat system is an easy and flexible way to hang virtually anything on a wall. While it has been mostly used in hanging cabinets it can be used to hang shelves, pictures or racks for tool storage. It's generally a 3 to 4 inch wide (3/4 inch to 1 inch thick) piece of wood or plywood cut at a 45 degree angle. One piece gets securely mounted to the wall while the other piece of wood gets mounted to whatever it is you need to hang. Put the two together and you get a very secure connection. Lately they have been a ton of french cleat tool storage videos on YouTube but as Father Thomas from MonkWerks.org points out there are some issues when using the system for racks/shelf tool storage. But like any good woodworker he doesn't just point out the issue he provides a great workaround tip.
Check out his article & video: MonkWerks: French Cleat Clamp Rack
Thanks for the tip Father Thomas!