Oops! LOL yes I meant cloaca. Voice to text. My dad's wife and my niece are both audiologists, too! Anyway I hope the YouTube video is helpful for people.
Also, she was sexing the Barred Rock in particular and demonstrated several different ways, one of which was looking at the legs. The females have a dark wash on top of their legs and feet and the males do not. theirs are pretty much the light color through and through.
There is a YouTube video collection called Karen's Coop. She actually has several videos and one of them shows how to sex the chickens by looking at their cochlea (butthole). LOL or the differences in Wing feathers. It was pretty helpful.