Close a purchase order

I just want to close a purchase order. I have spent a half an hour and still can't find anything. I have the PO open and there doesn't seem to be anyway to close the entire PO. It looks like I have to go through every line and click closed. In QBMac, there was a little stamp at the bottom of the window that I could click and the entire PO would be closed. I do not see that stamp, nor any other option to close a PO.

Why, why, why is everything so difficult on QBO????