Use Retin-A exactly as your doctor has prescribed it for you. Follow all directions on your prescription label. Do not use this medicine in larger or smaller amounts or for longer than recommended. Do not take by mouth. Retin-A is for use only on the skin.
Definition of wall for English Language Learners : a structure of brick, stone, etc., that surrounds an area or separates one area from another : the structure that forms the side of a room or building
pillar (plural pillars) (architecture) A large post, often used as supporting architecture. Something resembling such a structure. a pillar of smoke. An essential part of something that provides support.