Originally Posted by Looigi

The magnets attract each other very strongly, but the surface is very smooth and slippery. To use them to fasten numbers it'd be better to encase them in something that has more friction so they won't slide and the number get pulled out from between them. You could cover them in some coarse fabric tape or something.

Originally Posted by Clipped_in

^^^I think that's probably right. I'll bet spraying them with Plasti-Dip would work.