Rack-mount keyboard holder

I have a portable monitor and keyboard that I use for debugging computers, and when not in use they need somewhere to live.

My [Vevor network rack](https://www.vevor.com.au/server-rack-c_10750/vevor-open-frame-server-rack-network-server-rack-12u-4-post-19-482mm-relay-rack-p_010882320112) has slots for cagenuts on the side, so I made this model to be attached to the side of the rack (two of them) to hold the monitor and keyboard when not in use.