@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.