Whenever you make an Intelligence (Investigation) check related to the of structure woodwork, you are considered proficient in the Investigation skill and add double your proficiency bonus to the check, instead of your normal proficiency bonus. This can be used to spot irregularities in wooden walls or floors, making it easier to find trap doors and secret passages. You can quickly assess the weak spots in a wooden floor, making it easier to avoid the places that creak and groan when they’re stepped on.