Maybe I'm really missing something fundamental here, but it seems to me that there are more hog ring pliers than there ever were hogs. They seem to be everywhere. Why so many?
Once upon a time, every farmstead had hogs; hogs will root & so every farmstead had hog ring pliers -- if you mislaid your first - third pairs they were cheap enough.
When I was a kid going to farm sales with dad there'd be multiple hog ring pliers in the "hay rack lots" on every sale. Dad had lots of different styles of hog ring pliers -- there is still a shelf full of different brands of hog rings because the auctioneer didn't think they'd bring anything when dad sold his tool collection. There may be a shoe box worth of hog ring pliers laying around yet as well -- all rusted solid and only good for scrap metal.
I used them for upholstery work, & clip wire cages together. but how do they use them on Hogs? "Hogs will root"?
"Root hog, or die." Hogs use their snouts to "root" i.e. dig in the ground to look for food, turn up cool soil to lay on, etc. When you have hogs penned up, they will dig impressive hog wallows, dig themselves through or under fences, etc. The hog rings were installed in that combination of gristle & sensitive tissue that comprises a hog's snout to make rooting uncomfortable and hence discourage rooting.
Patent no 47,329 (
http://www.datamp.org/patents/displayPatent.php?pn=47329&id=50033 ) shows a hog's snout with one such wire in place . Patent no. 116,440 (
http://www.datamp.org/patents/search/advance.php?pn=116440&id=32374&set=29 ) shows a different style & location for placing the ring. Patent no. 154,046 (
http://www.datamp.org/patents/search/advance.php?pn=154046&id=42296&set=46 ) shows yet another notion.