The elevation of working platforms of trestle and extension trestle ladder scaffolds shall not exceed 20 feet above the ground, grade, floor or equivalent surface.

Where the working platform of any trestle ladder scaffold is located more than 10 feet above the ground, grade, floor or equivalent surface, the tops of such trestle or extension trestle ladders shall be tied in to the building or other structure. Such tie-ins shall be by means of rigid bracing, chains or ropes fastened securely to substantial, firm anchorages. Where such anchorages are unavailable or where such tie-ins are impossible and there is no adjacent wall, the bases of such trestle ladders shall be extended perpendicularly to the length of the working platform such distance as to provide a base dimension of not less than one-quarter of the height of the scaffold platform above such base.

Working platforms between trestles shall be equal to the width of the rungs of the extension. Where ladder type platforms are used, such platforms shall comply with the requirements listed in Table XIII of this Subpart.

Trestle and extension trestle ladder scaffolds shall be used only for interior painting, decorating, light maintenance or similar work. Such scaffolds shall not be used for exterior work nor for work in which the equipment, supplies or materials required may hamper or endanger the persons on such scaffolds.