It is a DIY rigid lithium ion battery test slot for high current / high temp operations. I used M3 insert and M3 bolt as terminals. It can be used from 18650 to 21700 high current battery sizes. I designed slotted air gaps for better heat dissipation. I hope you will like the design.

Insert Link: M3xD4,6XL3,0
https://www.aliexpress.com/item/4000232858343.html?spm=a2g0o.order_list.0.0.21ef1802BK0qTY

OR;

Use M3 nuts and bolts