Section R. 408.41128 - Single-cleat ladders; width; side railsRule 1128.
(1) The width of a single-cleat ladder shall be not less than 16 inches or more than 20 inches between rails. Side rails shall be parallel .(2) Side rails of a single-cleat ladder shall be not less than nominal 2-inch by 4-inch construction grade lumber for ladders less than 16 feet in length and not less than nominal 2-inch by 6-inch construction grade lumber for ladders from 16 feet to 24 feet in length .Mich. Admin. Code R. 408.41128