The hole was originally a talon lock, a pin was but through the sheath and the knife securing the knife in the sheath. The TOPS Storm Rider has the same thing except it's on the butt of the handle. The hole has now just become part of Jerry's trademark. Hope this helps.
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"Better to reign in Hell, than serve in Heav'n"
John Milton
There are only two types of people; those who understand this, and those who think they do.