I edit lots of event video and need to keep archives of all projects. Once project is finished I transfer all project files to external HDD's. I have a stack of 16 HDD's currently (and growing) and wanted a way to easily be able to just pull a drive out of the stack.

These trays are modular. The pins on the top slot into holes on the bottom. I'm still printing them at the moment but see no problem with stacking 8 together. Very sturdy and solid and there is a lid to pop on the top which slots into the same pins. I also added rubber bumpers to the bottom most tray to stop the rack from sliding on a desktop.

Edit:
Have added a version without the hole at the back - you never know.