46 C.F.R. § 160.017-13 – Construction.

(a) General. Each chain ladder must have two suspension members. Each step in the ladder must be supported at each end by a suspension member.
(b) Suspension member. The distance between the two suspension members must be at least 400 mm (16 in.), but not more than 480 mm (19 in.). The chain between each top lashing ring and the first step must be long enough so that the distance between the center of the lashing ring and the top of the first step is approximately 600 mm (24 in.).
(c) Lashing rings. A lashing ring must be securely attached to the top and bottom of each suspension member. The means of attachment must be at least as strong as the chain and the lashing ring.
(d) Thimble or wear plate. A thimble or wear plate must be attached to the chain where it can slide on its connections to the lashing rings.
(e) Steps. Each step of a ladder must have two rungs arranged to provide a suitable handhold and stepping surface. The distance between steps must be uniform. This distance must be between 300 mm (12 in.) and 380 mm (15 in.).
(f) Rungs. Step rungs must meet the following requirements:
1. (1) Each rung must be wooden, or a material of equivalent strength, durability, handhold, and step surface characteristics.
2. (2) In order to provide a suitable handhold and step surface, the width of each rung must be at least 40 mm (1 1/2 in.) and the thickness must be at least 25 mm (1 in.), but not more than 40 mm (1 1/2 in.).
3. (3) The distance between the rungs in each step must be uniform. This distance must be between 40 mm (1 1/2 in.) and 65 mm (2 1/2 in.).
4. (4) Each rung must be attached to a spacer ear by a method that prevents the rung from rotating and that supports it in a horizontal position when the ladder is hung vertically.
(g) Spacer ears. Spacer ears must meet the following requirements:
1. (1) All spacer ears on a ladder must be the same size and shape.
2. (2) The top and bottom of each spacer ear must be attached to a suspension member.
3. (3) The top point of attachment must be at least 100 mm (4 in.) above the top surfaces of the rungs attached to the spacer ear.
4. (4) Each spacer ear made of sheet metal must have features such as formed ribs, rolled flange edges, and stress relief holes at the ends of cuts, to prevent the ear from bending or tearing.
(h) Fasteners. Each fastening device must have a means to prevent the device from loosening.
(i) Workmanship. A ladder must not have splinters, burrs, sharp edges, corners, projections, or other defects that could injure a person using the ladder.