I recently went on the foundation skills BCUK course (very good course) but was rather embarrassed at one point when – on the overnight camp – my knife came out of its sheath and I couldn't find it. This then necessitated a torchlight search with several other people, in the dark. Fortunately we found it without anyone coming to any harm. The next day the knife fell out of the sheath when I was under my tarp.
This may be a particular problem for me because I usually wear the knife around my neck. It may arise when I swing the sheath and knife over my shoulder to keep it out of the way when doing something else.
I have searched the BCUK site and not found any specific solution to this issue other than to get a new (usually leather) sheath.
So here is what I came up with.
First a general view of the type of sheath. (The rubber inner tube on the body of the sheath has been there for ages and serves as an emergency tinder/rubber band etc, and also keeps an emergency cigarette lighter and short length of Duct tape underneath.)
The ‘mod’ – if this actually warrants the name – was to super-glue a rectangular piece of bicycle inner tube on the inside of the semi-circle and then cut it to shape. I have stuck a piece of yellow paper on it to help highlight it in the next picture.
I can’t guarantee that the knife won’t actually fall out accidentally anymore but it certainly seems a tighter fit and won’t make the problem more likely to recur.