Does anything like this exist? What would be the best search terms to find it for sale. I'm after something lighter weight, and cheaper, than aluminium extrusion for low-stress structural frames (holding lights, frames for little thermal enclosures round 3d printers, structures within robots...), with the same sort of groove structure and shape which lets you fit T-nuts in the grooves and mate on to the kinds of corners and other attachments you can use with aluminium extrusions. Thanks