Generally. Every below-ground pool shall, at all times, be fully surrounded by a substantial fence, wall or other enclosing structure (or barrier of thick set hedge approved by the Construction Official) not less than 48 inches in height and grade, so constructed as to prevent effectively unauthorized access by children. Said structure shall not have openings, holes or gaps larger than two inches measured horizontally, except for doors and gates. The doors and gates shall also be of substantial construction and not less than 48 inches in height and grade, and shall be equipped with self-closing, self latching locking devices, capable of keeping such doors and gates closed and locked at all times. Such doors and gates shall be kept locked except when the pool is in authorized use.