Thankyou Birdman. I attach my collars with Devcon long set epoxy. I use a dremel with a medium to coarse stone to clean and rough the interior of the collar. Then the leather surface is sanded and roughed with 100 grit paper. The epoxy is applied to the collar and slipped on. Excess epoxy is cleaned up, and the knife, or a spacing block is inserted until the epoxy has a good set. I use only carving grade vege tan leather for these. You could run into problems with oil tan, but with vege tan the epoxy soaks into the leather enough to make a strong, lasting bond. The collar itself is made to have a snug fit. Moisture is not a problem, unless maybe it was submerged for a long length of time, which would creat more problems than a loose collar. If one wanted to go more PC, they could be attached with pitch and, or, small brass, or matching pins, clinched over on the inside, and neatly dressed off on the outside. I have seen this on a couple of old sheaths. I don't see this as necessary, but am not adverse to doing them that way. From the testing I have done, there is no stronger glue for leather than epoxy, when strength is an issue. In every day common use, the collar itself takes the majority of any stress, while the leather is merely a protection for the blade. Probably the best, but more work involved, is the type made of wood with a covering of thin leather, having the collar attached by small nails that are dressed off and nearly invisible. Not that difficult to do, but much more time consuming. Even with these, a little epoxy under the collar does no harm.