Cultivators, tedders, plows all attach correctly, but I can't get seeders to attach because it has a different attachment.

In particular I was trying the Hammer Cornking, is there something that goes with it? I know the other seeder, Lemkin? has two parts, but I didn't see that with the Cornking. Did I miss reading it somewheres?

What am I missing?

Thanks! I knew I was missing something easy.