Hat on a crab

Hat on a Crab is an idiomatic phrase that describes someone who lacks the ability or knowledge to perform simple tasks or understand basic concepts, implying a sense of incompetence or cluelessness in their actions or understanding. This expression is used metaphorically to portray an individual's incapacity or lack of aptitude in accomplishing elementary tasks or comprehending straightforward ideas, highlighting their overall lack of competence or familiarity in the given context.

When it comes to cooking, Lisa is like a hat on a crab - she can't even boil an egg without burning it.

Sarah's lack of basic computer skills makes her a hat on a crab in the office.