Let them come, then let them go

• Hold out your arm at arm’s length
• Make a circle with your thumb and index finger
• Look through the circle at an object on the other side of the room
• Now slowly bring the circle back to your eye, such that your fingers never obscure the object, and it’s always centered in the circle

Which eye did your circle arrive at?

!That’s your dominant eye!<

Edit: formatting, I’m a Markdown dumbass

Musician’s earplugs

It can also be used to mean a singular cogged wheel

Half of software engineers don’t know what a POST is either