These brackets slot into the wall standards and support the shelf from beneath. They are made from strong steel and are finished with a grey epoxy paint. You will need one bracket for every wall standard that each shelf passes. So the quantity depends on the layout that you create. If you have one shelf stretching 4' (1.22m) wide, you will need three brackets, as it should pass three wall standards. Once you have your shelving system set up, your maximum load shelving will be able to support up to 600lbs per 6' shelf. Thats an incredible 43 stone for every 1.83m shelf!