Get a girl from behind while she's bent over the bed facing the window, then you come up with an excuse to pull out and tag your buddy in without her knowing. Quickly go outside, and knock on the window.

When someone goes to the gym and spends 90% of the time on their phones scrolling through social media

The act of banging in front of a window with the hopes of being seen; most commonly exercised in the form of hotel sex.