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.
When handballs become "dead," or no longer bounce freely, they may frequently be restored by inflating them with air. This can be done by means of a bulb attached to a hypodermic needle. The needle must be inserted through the soft plug which every inflated ball has, and which can be discovered by pressure. After the ball is inflated and the needle extracted, the soft rubber closes around the fine hole, preventing the escape of the air. If a leak is found, which allows the air to escape too rapidly, a repair can be made with a single-tube tire outfit. - Contributed by A. B. Wegener, Camden, N. J.