What is "uprights"

Usage examples of "uprights".

A tiny swell of breast, ribs I could count, one, two, three, four, five, and the smooth concavity of my stomach, slung like a hammock between the uprights of my hipbones.

With bleating cries they ran away from the Uprights and their fire, abandoning the antelope.

They forced their way right through the cluster of Uprights, who hailed stones and bone spears at them.

The Uprights fell on her, and she went down in a forest of flailing arms.