support
A leg to stand on.
This idiom or expression means:
Supporting material.
When someone says “He doesn’t have a leg to stand on,” they mean something like “He doesn’t have enough data to support his theory,” or “He doesn’t have an alibi to help him in his defense,” etc.
Having someone’s back.
This idiom or expression means:
Supporting someone.
Watching someone’s back for support.
A. Hey Joe, I don’t know if I should do this?!
B. Go ahead, I have your back. I’ll help you if necessary.
