put hand up
put (one's) hand up
To hold one's hand in the air to indicate that one wants to answer or ask a question. Don't yell out your questions, kids, put your hands up! I do raise put my hand up in class, Mom, but the teacher never calls on me!
put one's hand up
to raise one's hand to get attention from whomever is in charge. The student put his hand up to ask a question of the teacher. She put up her hand to ask a question.