These are modular driver bit holders, hopefully self explanatory.

Each module is 70 mm long and can be combined as needed.

There are three sizes of the bit holder modules. The clamping block is a single size, but there are two versions, this is so you can put a clamping block on the end and not have the knobs poking out. You'll see what I mean. 

• Short holder – holds bits up to approximately 60 mm long
• Medium holder – holds bits up to approximately 130 mm long
• Long holder – holds bits up to approximately 200 mm long

Short bits can be stored in the upright holders, which are available in capacities of 8, 16, or 24 bits.

A video showing it: 

Screws I used are here: [https://www.aliexpress.com/item/1005008141974255.html](https://www.aliexpress.com/item/1005008141974255.html)

I'm also planning a couple variants on this model but would like some feedback on this design first. One variant would have magnet slots, and the other would be a stiffer version so you can better move it around outside the toolbox.