I thought bottle caps would make pretty cool magnets, but the question was what to put between the back of the cap and the magnet... That's where the clay came in. I was also making some bottle cap checkers, and had some clay leftover from that, so I just used what I had. Here's how I did it.

Step 1: What You Need

- Bottle caps
- Clay
- Butter knife
- Magnets
- Glue

Step 2: Cut and Fit Clay to Lids

Roll the clay out into 'logs' around the size of the bottle caps you're using, then cut them close to the size you'll need to fill in the hollow part of the cap. Add or remove clay to make it fairly even with the sides. Allow the clay to dry.

Step 3: Coat Bottoms With Glue

As sort of a sealant, add a layer of glue to the bottom after drying. You'll want to add the magnets at this point if they're not self-adhesive, and maybe even if they are. Either way should work. Allow the glue to dry.

Step 4: Cut and Add Magnets

Cut your magnets to the appropriate size, then stick them in place. Since my magnets were on a roll, they were a bit curved, so I put them under a weight for a bit to try to flatten them out.

Note: If you're using the bigger lids, you may want to make sure your magnets are fairly strong to compensate for the extra weight of the clay, or else you may have magnet 'sliders'.