PTO pump shaft question

[HappyCPE]

I am the proud owner of an 8 roller PTO pump. This is my first one, and I got a "kit" with the arm, spring, chain, etc.

Now my question - The pump shaft has a groove, to accept a kind of key. They included a collar to attach to the tractor PTO, which also has a groove to accept a key. This groove has 2 set screws in it, as if to lock in another piece of metal. That other little piece of metal is missing. Essentially I have 2 female components and the only way they could ever mate is to drive the set screws into the pump shaft; that can't be right. Did they forget a part? They forgot to send nuts along with the bolts so it wouldn't surprise me if someone in China has extra parts, like a 3" long x 3/16" square key, left over.

Did I mention I'm new at this?
Please, no jokes about the latest wave of California weddings!
Thanks.

Edit - Apologies about posting this here instead of under Attachments.

 

[wedge40]

The shaft on the pump should have a "groove" in it to accept a key. This key will either be a square piece of metal or something that look like a half circle. The other piece should be able to slip over the pump shaft and it too will have a groove in it to accept a key. You would put the key (which should be included) into the groove on the pump shaft and the slide the other part over the saft making sure the grooves line up. this should be a tight fit and may need a little persuasion with a rubber mallet or peice of wood and hammer. Once this is done tighten the set screws and it should be ready to use.

Wedge

 

[HappyCPE]

OK, thanks. You confirmed that I'm missing the key. Off to the shop again....

 

[wedge40]

OK, thanks. You confirmed that I'm missing the key. Off to the shop again....

TAKE THE PUMP!!. There are many size keys. They will be able to fit it properly.

Wedge