Took off the stump jumper and blades off my old bushog. In the shaft at
the bottom was a piece of metal I assume is a keyway. Although the only
key ways I have messed with were square. (This was an odd shape).

How would this key way hold the stump jumper on? In the stump jumper I
could not find a "notch" I would expect for the keyway.

Any help would be appreciated!