4-Channel Relay Module Case

This is a remix of @thehair's version (https://www.thingiverse.com/thing:957292).

Even those 4-channel modules look quite the same, there seem to be little differences in spacing of components.

This case is adapted to [this one](https://de.aliexpress.com/item/1005002867727977.html) on AliExpress.

I adjusted the board mounting on bottom part, moved holes on upper side to align with pcb components (connectors and leds) and added clips on each side to the upper part to help with alignment to bottom.

**Update 2023-07-23**
Since I do not need air gaps in bottom part, I removed them. But I added a version with air gaps for those who need fitting bottom part and air gaps.