x2
When I was learning as I was earning (yeah, right... chicken eggs), there were certain machines on the yard that would require PTO couplers. Sometimes I'd forget which machine needed it, and I'd just safely test it before actually going out and using the implement. If I did, I'd grab it off the other machine. The old man was cheap, that we only had 2 couplers and if I recall, 3 out of the 14 machines needed it.