Hole in One

This is a simple variant of the “hole in one” tool to accurately drill holes for electrical outlets through drywall or other sheet material. 

The “inside” part is placed in the electrical box you need to find before the sheet is mounted. The “outside” part connects through the sheet with magnets. The hole in the middle of the "outside" part guides the center drill of a holesaw to the correct position

I used 10x3 mm magnets for this, but I have uploaded teh .f3d file so it can be altered in Fusion360