![mokey bars mokey bars](https://www.foreverredwood.com/image/catalog/product/sheldons-monkey-bars/6619-sheldon_s_monkey_bar_set-douglas__1_1_-_edited_1_1.jpg)
^ DISTRICT OF COLUMBIA APPROPRIATION BILL FOR 1939 HEARINGS BEFORE THE SUBCOMMITTEE OF THE COMMITTEE ON APPROPRIATIONS UNITED STATES SENATE.^ a b "'J' is for Jungle Gym" from Winnetka, Illinois Historical Society.^ Hinton's original patents for the "climbing structure" are U.S.The American National Safety Council recommends that playgrounds have at least 12 inches (30 cm) of such material and since 2011 has banned the use of woodchips. To reduce the risk of injury from falls, jungle gym areas often have a thick layer of woodchips or other impact-absorbing material covering the ground. Thus, the abstraction of Cartesian coordinates could be grasped as a name of a tangible point in space. When Sebastian Hinton was a child, his father, mathematician Charles Hinton, had built a similar structure from bamboo with the goal of enabling children to gain an intuitive understanding of three-dimensional space through a game in which numbers for the x, y, and z axes were called out, and each child tried to be the first to grasp the indicated junction. The term "monkey bars" appears at least as far back as the 1930s, though Hinton's initial 1920 patent appeals to the "monkey instinct" in claiming the benefits of climbing as exercise and play for children, and his improvement patents later that year refer to monkeys shaking the bars of a cage, children swinging on a "monkey runway", and the game of "monkey tag".
![mokey bars mokey bars](https://i.pinimg.com/originals/45/32/50/4532503806b41c16dcab2b2a9fc5c90c.jpg)
Hinton's second prototype "jungle gym" is still standing at Crow Island School in Winnetka, Illinois.
![mokey bars mokey bars](https://cdn.shopify.com/s/files/1/0040/2358/2835/articles/Monkey_Bars_for_Your_Kids_1200x1200.jpg)
It was sold under the trademarked name Junglegym™. The first jungle gym was invented in 1920 and patented by lawyer Sebastian Hinton in Chicago.