PTO = Power Take Off
it's the splined shaft that comes out of the back of a tractor. It's used for running other machinery, like a hay baler or auger or sickle bar mower
Agree, it's a replaceable tooth off of a digging bucket of some kind,
trackhoe, backhoe, loader bucket, or dragline bucket as dozerdan
said. They attach to the bucket on
the frog, a metal piece that is permanently welded to the bucket.
When the tooth wears out, you detach it and attach another with
a small weld or by heating the prongs on the wide end and pounding
them into depressions on the frog. That is how it works on my backhoe
anyway.