This specification covers the construction of standard and custom-built interior steel doors and frames for ships including U.S. Coast Guard certificated vessels with domestic routes. Doors and frames are to be hollow metal construction with the door insulated for sound or fire. The doors are intended for use in staterooms, lavatories, passageways, and other areas protected from weather. The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other.