I didn't realise Quest aims with only his left eye open while playing pool. Hegemony and I aim with both eyes open. Then I was asked which eye of mine is the master eye. I assumed that it was my right eye, but Hegemony got me to test it out. The trick is to form a triangle with the thumbs and index fingers of both hands, and keep your arms outstretched before you. With both eyes open, focus on something which appears within the triangle. Then take turns to close either eye. The object of focus will disappear if you're looking with the non-master eye. Eh. And so my master eye turned out to be my left one instead. They were surprised I didn't know this test, but I guess it's something they picked up from National Service.