(a) Each crib or play yard (also known as a play pen), whether provided by the home or the child's parent, must have a firm, flat mattress that the manufacturer designed specifically for the crib or play yard model number that snugly fits the sides of the crib or play yard. You may not supplement the mattress with additional foam material or pads.(b) Each crib or play yard must be bare for an infant younger than 12 months of age, except for a tight-fitting sheet and a mattress cover to protect against wetness. The mattress cover, whether provided by the home or the parent, must:(1) Be designed specifically for the size and type of crib and crib mattress that the cover is being used with;(2) Be tight fitting and thin; and(3) Not be designed to make the sleep surface softer.