BTU-saving entry/exit
Refers to a K1-saving action that you take during colder weather, and consists of rapidly opening the front door of a home/business only as far as you need to in order to quickly slither through, and hastily slapping the door shut again to minimize heat-escape.
Small barber-shop owner: Most of my customers don't seem to realize that it really costs me a pretty penny to heat my place of business... they leisurely take their sweet old time to amble in and out, and just let the door gradually close on its own. A few thoughtful/aware folks, though, do diligently employ the "BTU-saving entry/exit" procedure when passing through my door, and I really appreciate that.