Horizontal rails?

So far nearly everything in this project and nearly all builds are using vertical posts. Things like shelves depend on gravity to hold their contents, etc.

Should it be a goal to be able to mount these racks with horizontal rails and vertical components? Or if not a goal, at least indicate which things won't work that way, and/or aim to produce designs that will.

Note: the eurorack and DIN standards mentioned in #32 #47 have horizontal rails and vertical components and that seems pretty nice. It would allow for more flexibility for where you could put miniracks.

Start by reviewing the existing rack designs and the eurorack and DIN discussions in #32 and #47. Establish whether horizontal rails with vertical components are in scope, then identify which existing designs would need support or documentation of incompatibilities.

Written by the indexing model from the issue text.