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.
An adjusting device for a vaulting pole that can be easily fixed at any point on a round pole by using a wedge and ring, is shown in the sketch. The wedge carries a pin on which to place the cross pole. The manner of using this device as well as its construction is clearly indicated. - Contributed by Sterling R. Speirs, St. Louis, Mo.
Ill: The Ring on the Upright, Held in Position by the Wedge, Which in Turn Carries the Pole on the Pin