Help with sexing chicks

if youre going to a farm store, they should be marked as pullets or straight runs. Get the pullets

 

If you are getting barred rocks...I read that the females have the black down the front of their legs. The males don't have any black on their legs. I have one with no black on his legs and his colors are much more distinct at only 3 weeks. Don't know if its true but its worth a shot.