(1) You must make sure rungs have a minimum diameter as follows:

(a) Rungs of wood ladders are at least one and one-eighth inches.

(b) Rungs of metal ladders subject to unusually corrosive exposures, such as individual metal rungs imbedded in concrete which serve as access to pits and to other areas under floors, are at least one inch.

(c) Rungs of all other metal ladders are at least three-quarters inch.

(2) You must make sure rungs, cleats, and steps are spaced so the distance from the centerline of one rung to the centerline of the next rung does not exceed fourteen inches, or is less than ten inches (see Figure D-2 in this section). Ladder rungs in elevator shafts must be spaced not less than six inches (15 cm) apart, and not more than sixteen and one-half inches (42 cm) apart, as measured rung from rung centerline to the next centerline (along the ladder side rails).

(3) You must make sure the minimum inside clear width of the stepping surface of rungs, steps, or cleats is sixteen inches (see Figure D-2 below).

(4) You must make sure individual rung or step-type ladders have rungs or steps that are shaped so that a person's foot cannot slide off the end (see Figure D-4 below).