@neverdie, a very very easy handling. Just heat and melt them in the PLA :)

I use longer M3 bolts so that I can heat them up (in a flame of a stove or lighter)
and able to position them very accurately into the holes which are already there in the case it self. The knurled inserts have 5mm of diameter and I'm designing the holes @ 4.8 mm. If the inserts are heated you will melt them into the 4.8 mm holes and after cooling down...it solid and fixed in the case.

@dbemowsk ], yes it's a fully printed case using PLA material.
I bought some nice and decent brass knurled from Banggood. Bought directly some M3 bolts made of stainless steel also at Banggood.The bolts you can get in different lengths.

@gohan Thank you! Although I have some warping on one of the corners unfortunately.

Finalised my indoor weather station with light intensity measurement build around a WeMos D1 mini. The system is using a BME280 module for pressure, humidity and temperature measurement. The light intensity is using a normal plain good old LDR.
Step down converter to convert input voltage towards 5 Volt.
Of course using the esp8266 MySensors solution! Great achievement to all involved in building it. Really awesome!

Case designed in Onshape and printed on a Ultimaker 2+.