Know your stuff
Meaning: to know a lot about a subject, or to be very good at doing something, be experienced or knowledgeable in one's field or in the matter at handalso, know one's onions
Example: She's an excellent teacher - she really knows her stuff. Patrice knows her stuff when it comes to Mexican history, or We need a handyman who knows his onions.
Example: She's an excellent teacher - she really knows her stuff. Patrice knows her stuff when it comes to Mexican history, or We need a handyman who knows his onions.