Hi Steve
Yes very similar to that. It’s 6 x 20mm circular rare earth magnets. I bored 3 holes (2 magnets per hole) with a Forstner bit so there was less than 1mm wood between the magnets and the surface. I saw something similar on this woodworking video:
https://youtu.be/Szm-pnU3raM
The inclinometer seems to hold quite strongly.
Rod.