monkey bars

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun plural A structure of poles and bars on which children can play, as in a playground; a jungle gym.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A jungle gym
• noun A row of bars, found on playgrounds, under which one hangs by the arms and crosses by swinging between bars, legs dangling down, like how a monkey might move across.