The habaki of the iaito is the collar of the sword which fits snuggly into the koiguchi, or the mouth of the saya. It should because of this tight fit, when fully sheathed, prevent the sword from tipping out and requires a push from the thumb to start the drawing process.After much practice the sword feels loose in the saya as the bottom edge is worn away. To maintain this tightness a small piece of wood needs to be glued in place. This article outlines how I went about my koiguchi repair.
Firstly I found a nice piece of veneer: mine was cherry, a bit thick probably at about 4/5mm but I'd rather too thick than than too thin! I cut a wedge shape out of the veneer and glued it in position with PVA wood glue and left it to dry. My tip for gluing is to use a pin! Squirting it directly form the bottle may end up in a blobby mess on your tiny bit of veneer!
Roughen the inside top edge of the saya and tap out the dust. Glue it in place and leave. Once it's dry simply use a file to bring it down to the desired level: remember it should help maintain the sword in the saya without it being too difficult to push out. Mine is a bit too stiff at the moment so I'm working it in slowly with some drawing practice.
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