Designed to hold two small breadboards and provide a firm mounting location for any of the ST Micro ARM MBED Nucleo boards. I like to have my breadboard and development board in a single package to facilitate moving projects.

I use small brass threaded inserts (3mm) to provide attachment points for both the Nucleo board as well as having the ability to attach a panel at the rear of the breadboard assembly to hold project specific things like potentiometers, banana jacks, etc...

All of my bread boards are designed to utilize component panels such as those here:
https://www.thingiverse.com/thing:2439398

The design was done in Fusion 360 and includes the design file if you wish to make changes.