Let's picture this scene: you're walking along on the pavement. Another person is walking along on the pavement opposite, heading in the opposite direction also. Said person checks you out. You notice said person checking you out and also happen to check said person out, realising that they really look quite lovely. And attractive. And have a nice bum. Etc etc. You continue checking each other out, whilst slowing the pace of your steps, until you pass each other and you'd have to turn around to continue. Nevertheless, after a few steps of not looking, you decide to glance around subtly. You both do this at the same time. You laugh.