Who has never pulled a push door? Or pushed a door that is supposed to be pulled to open? If it is a basic knob, it’s hard to know which way it opens.So how about changing the shape of a doorknob to add small constraints on the push/pull actions so that a user can easily notice how to open the door? (I said “small constraints” because there are times when you have to pull a push door and push a pull door, such as when the door is stopped with a door-stopper.) This would be my solution: