It sounds like advice from an American Old West tough guy. The practice dates back to 1200 BCE to around 300 BCE in Greece. It revolves around the idea that you want to know who enters the door. It’s good business advice too.

When one enters a room, an outside door, or an archway, one participates in a transformative experience. You move from one state of mind to another. You transfer from going to being in. Doors have long been seen as transition, change, and opportunity symbols. We cross a threshold into a new space or situation through a door. However, have you ever noticed how one pauses when going through a more elaborate door or entrance? This can represent a fundamental shift in our point of view. 

Going through a door can also be an opportunity to practice mindfulness. Entering a new space with intention, meaning, and focus sets the tone for everyone.

Finally, it can be part of a ritual or ceremony. For example, some cultures have you remove your shoes and knock before you enter. In Western traditions, all eyes are on the groom and the bride as they enter a space.

As the one facing the door, you receive all the benefits of seeing their body language, demeanor, and more. You can acknowledge them, greet them, rise, and be deferential or perhaps bow. There are many ways to enter a room. You can also manage the situation in many ways. It sets the tone for any interactions by being prepared. 

Your “first contact” with them can let them know your level of engagement. Looking back down quickly at your phone or some other distraction tells them you are uninterested. Open body language, regardless of facial expression, invites them in. 

It’s a lot to pack into where you sit in a room—the power dynamics of your place in the room shift with culture and our age. For example, in times of the first cities of Sumer (4000 BCE – 1900 BCE), rooms were empty until ready to be used.