This is a simple fridge mounting sliding tracker, intended for kids chores, but could be useful for tracking any binary task or activity. 

I also wanted the slider/button to be big enough to cover some text (i.e. a childs name). There is heaps of clearance behind the slider/button to apply an adhesive label, or you can write directly on the surface with a Sharpie. 

For magnets, I used 5mm(dia) x 6mm(long) round magnets, but you could also stack the commonly available 5x2mm. I found in the single, this gives a pleasant amount of holding power to the fridge. In the larger versions you may be able to reduce the number of magnets depending on how firm you want the grip to be. The holes are 5.4mm diameter, which on my printer provides a nice friction fit for the magnets without risking cracking the walls.

I've included multiple models from 1 high to 4 high.

All files will print in the default orientation, 0.40mm nozzle recommended.