I created this so no glue is needed to add the HDD tray. It can be put in the same 19" shelf as the design the object was remixed from.

The basic idea is that the corners of the original frame are removed and the new piece slots into the void. The threaded rod holds the piece in place.

the raspberry pi mounting tray and rack mounting "ears" from the original design this is remixed from are unchanged and both can be found there.