N.J. Stat. § 19:8-12: Size and construction of boxes

The boxes shall be at least one foot in depth, width, and length, measuring the same on the exterior thereof, and shall be constructed with wooden or metal tops and bottoms and wooden or metal frames and glass or metal sides.

Each box shall be provided with a door at least six inches square on the top of the box, which shall be secured by not less than three locks, no two keys of which shall be alike, and shall have an aperture measuring at least three inches by one-half inch and not more than six inches long by one inch wide for the reception of the ballots, and a device which will close said aperture when the election is over or when the box is not in use, which device shall be so constructed that it cannot be operated without first opening the door of the box. The box shall have no stamping or marking devices.