Instructables

Step 4: Add Blu-Tack

To (try to) replicate the temporary adhesive qualities of the Post It note I used Blu-Tack.  Just roll out 1-2 small balls of Blu-Tack and stick it to the back of each of your reusable notes near the top. 

Removable glue dots can also be used instead of Blu-Tack as it doesn't leave any residue behind, thanks to browsercat for the suggestion.

Before I thought to use Blu-Tack I considered taping paperclips to the back or using small magnets, but there would be limitations to where you would be able to stick it.  I haven't had much experience using Blu-Tack but it does seem to do the trick though it sometimes leaves little blue bits behind and I'm not sure if it deteriorates with time.