(1) Strength.

Every boatswain's chair and supports shall be capable of sustaining four times the maximum weight intended to be placed thereon.

(2) Chair or seat.

Every boatswain's chair or seat shall be suspended from its four corners by means of rope slings. Such chair or seat shall be not less than 24 inches in length by 10 inches in width. Such chair or seat shall be two inches in thickness except that such thickness may be one and one-eighth inches if the chair or seat is constructed of hardwood. Each such chair or seat shall be reinforced across its full width by means of cleats securely fastened to the underside of each end.

(3) Suspension tackle.

The rope used as a means of suspension for boatswain's chairs shall be first grade manila at least five-eighths inch in diameter or synthetic fibre with a breaking strength of 5,000 pounds and with a diameter of at least one-half inch. Such rope shall be reeved through proper size ball bearings or bushed blocks. Rope attachments to such blocks shall be by means of thimbles and splicing. Only safety hooks shall be used.

(4) Anchorages.

The means of suspension shall be attached to anchorages of sufficient rigidity and of ample strength. Where necessary, ropes shall be protected against chafing.

(5) Seat guard or safety belt.

Every boatswain's chair or seat shall be provided with a rope or strap guard across both the front and rear located 18 inches above the seat or shall be provided with an approved safety belt with separate hanging lifeline securely attached to a fixed support or anchorage in compliance with this Part (rule).