I found it in a local hardward store catalogue. It is primarily meant to be used for making desks and furniture etc, but can be adapted for a rack. The connectors are sturdy plastic connectors that join corners or right angles etc, all you need to do it have the metal cut to the right length and then click it all together. I will try and see if they have a website to show you. They are in the UK, but you might find something similar in the US.
Aubrey.