When we'd had enough fun finding things to pick up, we moved on to Challenge #2: Measuring Magnets.
When we did this activity in my son's kindergarten class, we used little printed grids to measure how close the magnet had to be to pick up a paperclip. For home use, I figured we'd keep it simple, and the kids got a kick out of using blocks to measure with.
We discovered that the hole punch was a two-block-magnet, while the scissors were a three-block-magnet. And the big surprise was that the Magnatile was a half-block-magnet.