Today I needed to drill eight holes in the ceiling, so I decided to buy a 2D bubble level indicator and print a mounting for it to ensure that the holes are perfectly upwards directed. The mounting is fixed by an M3 button head screw, the bubble leveller by 10mm Spax type self drilling screws (id=3mm). It took me two trys to come to these dimensions. Soon I will also post a design for a capsule bubble level (Dosenlibelle in german, hope I translated it right). The inner diameter is designed for a Bosch uneo maxx, simply adapt the mounting bracket dimenstion if your drill requires something else than 35mm for a collar mounting bracket.

This works for drilling in the ceiling or into the ground. For drilling to walls you need only the one level indicator which is orthogonal to the drilling axis. It would have to be rotated 90 degrees around y.

Have fun with it!

PS: please note, that I enlarged the space of the M3 nut and also the rim around it, to ensure that the design I posted won't break at the same point where my second try broke (as seen on the picture).

Update: so, today the can level indicator arrived. Problem is, that it only works with the bottom facing down. So it is not usable overhead for drilling in the ceiling. Good news is that I successfully tested this design and it works great. One has to stop drilling for reading the levels, but it really avoids that you drill anything else as a right angle.