Shimming a saya is the prefered method for tightening a katana, wakizashi or tanto in its sheath.
You will need:
- wood veneer edging
- narrow flathead screwdriver
- your sword
Step 1: Familiarize Yourself with the Saya
There is no need to shim the entire length of the scabbard. The blade doesn't actually contact the inside of the sheath. The only point of contact should be between the habaki (the metal collar at the base of the blade) and the saya.