Knee-high meaning

I've known Brandon since he was knee-high to a grasshopper.

Speck's sector headquarters was abuzz with activity; the only private place to talk was the back porch overlooking a field of knee-high winter wheat facing a sun setting too early.

There was nothing at all within a few feet of him, aside from knee-high wild flowers waving happily in the spring breeze.

She was more casually dressed in leggings, knee-high boots and a shirt that fell to mid-hip.

Before her, the knee-high grass waved with a slight breeze of warning.