We generally recommend your shelf be at least 2" thick when using the aluminum bracket - for a standard installation, we advise never going thinner than 1 ¾ in thickness for your shelf at the absolute minimum. This is because the bracket itself is 1 1/2" thick, so you will need at least 1/8" of additional material on the top and bottom of your shelf to house and conceal the bracket. Just remember to leave yourself that 1/4" of shelf thickness when selecting your material. In general, it's best to leave at least 1/4" at the top and bottom of your shelf, since its far too easy to blow out 1/8" with the smallest movement. See below for a diagram of the recommended shelf thickness.
*If your shelves are thinner and you still want to make our system work for your project, fear-not! Head over to our Exposed Bracket Article for an alternative installation method for thinner shelves.
When using the steel bracket, we recommend not going below 3 inches since the smallest 10-gauge bracket is 2 ½ inches tall - see our article about maximum shelf thickness to learn more about how to set up your steel bracket shelf. However, when only using the glued version, there is the possibility to extend these maximum height limits considerably. Do note that the weight of the shelf may also play a role here. Remember to consider the downward force caused by the particular placement of objects on the shelf as well.