[See also: Cats and Dogs May See in Ultraviolet] Like the human retina, the canine retina contains other kinds of photoreceptors in addition to cones, called rods. These light receptors do not perceive color, but they are sensitive to light and dark changes, as well as shape and movement. And the ratio of rods to cones in the retina is much higher in dogs than it is in humans.
The distance between rungs, cleats, and steps shall not exceed 12 inches and shall be uniform throughout the length of the ladder. 1910.27(b)(1)(iii). The minimum clear length of rungs or cleats shall be 16 inches.
supporting ladders should be set at a 4:1 ratio (see Figure 1) from the foot to the top support. Each section of a multi-section ladder must overlap the adjacent section by at least 3 feet for. ladders up to 36 feet and 4 feet for 40 feet or longer extension ladders. For example, a 24-foot extension ladder will. consist of two sections each 12 feet long, but the maximum extended length will be 21 feet, because the sections over-. lap by no less than 1Â½ feet when the ladder is at maximum extension.