The Potter's Kiln
A potter fired her kiln and waited for it to cool.
Usually, this took a day. She planned accordingly.
One winter, the kiln stayed hot for three days — the cold air had sealed it somehow.
She had promised delivery. She could not open the kiln. She could not make new pots. She waited.
After that, she built a second kiln. While one cooled, she could use the other.