This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
A good way to mend partially broken felt or a felt hat is to hold a lighted match under the break and smooth out the crevice with the hand. The shellac in the felt is melted by the heat and runs together, mending the felt in such a way that the break is hardly noticeable. This method may also be used to mend felt articles in the laboratory.