If your talking about the one on the belt loop,
then it's for makeing it in to a drop sheath.
You get some 2" webbing (like the belt-loop)
about 2' long (and another Buckle). Run it throught the sheath buckle,
Over your belt and back to the sheath,
That way the sheath is below the belt line
(So it doesn't get in the way of backpacks, Etc...)
It's my perfered way to carry camping, and
how I carryied my BK2 for the year it was my camp knife.
You should try it.