shoe tree 
noun
A shaped block inserted into a shoe when it is not being worn to keep the shoe in shape.The best ways to find a shoe tree are luck, accident, or word of mouth....
- I found the second shoe tree a day after that, and the third one three days after that.
- This narrow, 180-foot-long assembly of cast-offs included shoe trees, crockery, wheels, hand tools, hardware, animal horns and masks from various cultures, nestled one after the other.