united states - What to do with students coming to office hours asking to check their homework?

As a teaching assistant (TA), how to handle the situation where a student comes to office hours asking to check their homework? I.e. the student hands in their solution to the homework and ask the TA to check for any mistake. Assume homeworks are worth somewhere between 20% and 50% of the grade.

If country-specific, I am interested in the United States. If field specific, I am interested in computer science, linguistics, neuroscience and maths.