MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
Not sure the magnets will be strong enough -- I wouldn't trust it. How about something "keyed" to the wider part of the top of the vertical so that the horizontal slides on from the back or front? Maybe locks in with a magnet or pin or small screw.