This is a compact rack for the Raspberry Pi's.
The boards are all placed vertically instead of horizontally. It consists of a single base and some small supports for each board. It's really easy to print and fits everywhere.
This rack supports these models:
It also supports 2.5" Hard Disks or SSD's.
There is enough space below for WIFI dongles (see the picture).
IMPORTANT: this rack needs Right Angle (90ยบ) USB power connectors and 2.5mm screws.
Print 2 supports for each board.
The author hasn't provided the model origin yet.