The phrase "not know your ass from your elbow" is a vulgar expression used to describe a person's lack of knowledge or confusion in a particular situation. There are several synonyms that can be used in a more polite or professional setting to convey the same idea. Some common alternatives include "out of your depth," "clueless," "ignorant," "uninformed," "bewildered," and "perplexed." These expressions are less offensive but still convey the same meaning that a person has little or no idea of what they are doing or talking about. Using these synonyms helps to communicate the same message while maintaining a level of professionalism or sensitivity to the situation.