...when you're refinishing a floor? My answer:
(aside from using it as a workbench)
Teeter it across the threshold like this.
It's funny, the moment I positioned the piano halfway in/out of the doorway, I thought to myself, "This would sure be a bad time to have an earthquake..."
The piano stayed like this overnight, as the urethane dried, and the next day, we had a 5.4 magnitude earthquake. I happened to be sanding the first coat of urethane on my hands and knees at the time, and stopped for a second with a disoriented feeling. My head was swaying back and forth, and I was thinking what a strange feeling the motion of sanding was giving me! It was that moment that Melinda walked into the den and said, "that's an earthquake!" I looked over at the piano, and it was swaying back and forth, much like my head. The entire thing lasted about 20 seconds, and the piano survived.