I wonder what the attachment holes are for too? Could it be an attachment to make the Waki into a fighting spear? I know HD has already stuck his Waki in a tree.
That's EXACTLY what I thought. But I can't quite picture them selling spear shafts. Then I wondered about an attachment to connect two of them into a double sword. No, I can't picture them selling that, either. Maybe an attachment point for a basket hilt? No, too long a handle for that to look right.
I'm stumped.