Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5376507.

Here is a quick and dirty way to keep your precious 0.1mm (or other) shim stock flat and easy to use for bed leveling.

1. Print
2. Cut a strip of your favorite shim stock no more than 20mm wide. (I use 0.1mm)
3. Put into holder

The holder should snap together, but you can use glue or tape to keep it closed. I put a dab of hot glue at the back of the shim to act as a nub to make retracting it easier.

Enjoy.