Mini ruler for electricians

I have been looking for a small, pocketable ruler with 71 mm pitches to make my job easier when I have to mark two 68 mm round fitting boxes in the middle of a wall.

The markings on the top of these rulers are spaced equally 35.5 mm from each other making this middle boxes positioning task a breeze. 

The bottom side markers are placed equally 5 mm distance from each other.

On top of that I have designed a thicker version to my buddies who wanted a version with built in level. I have used these levels. 

My favorite is still the 155 mm long thin one. I'm using it on a daily basis.

I have uploaded the Fusion 360 source file so you can easily alter my design accoring tio your needs.

Update #20230702: I have uploaded a mini version which is compatible with Ubiquiti AP's mini spirit levels.