Cal. Code Regs. tit. 3 § 1438.12
Standard containers for lettuce which are made of fiberboard shall be constructed with inner and outer side flaps which are attached to each end and side. The total width of the two side flaps shall not exceed the inside width of the container and, if closed after packing, shall be closed by folding the inner and outer flaps inward at the manufacturer's score lines which shall be above the inside bottom surface of the container at a point equal to the inside depth of the container. For standard container number 45A, if they are fastened in a closed position, the opening between the outer side flaps shall not average more than two inches for the entire length of the container, allowing a 10 percent tolerance for the containers in any one lot.
Cal. Code Regs. Tit. 3, § 1438.12