If you've ever bought a hat that was just a touch too small, or found that an old hat shrank after long storage, you will understand the value of a hat stretcher such as the Hat Jack. The Hat Jack is made of two pieces of curved wood with a metal apparatus between them that can be adjusted to fit your hat. They help keep the shape of hats that are wet or must be stored for long periods. They are also perfect for stretching out a hat that is just a little too snug.
Put warm to room-temperature water into a spray bottle and spray your hat inside and out. It should be damp, but not wet through or soaked. This will soften the material so it can stretch with less risk of tearing.
Adjust the Hat Jack to its shortest length and place it inside the hat, level with the band inside the brim. Turn the centre apparatus so the Hat Jack fits snugly inside the hat, then turn the apparatus one half-turn more.
Allow the hat to stretch and dry overnight. Remove the Hat Jack; do not shorten it. Try on the hat to see if it fits. If not, moisten the hat as before, and place the Hat Jack back in the hat. Turn it another half-turn, and allow it to stretch overnight.
Repeat the process until the hat is the correct size. Do not try to stretch a hat more than about 6 mm (0.25 inch). Any more than that is almost sure to tear the hat.