The human vertebral column is the vertebral column (backbone or spine) of the human skeleton, consisting of 24 articulating vertebrae and 9 fused vertebrae in the sacrum and the coccyx.he human vertebral column is the vertebral column (backbone or spine) of the human skeleton, consisting of 24 articulating vertebrae and 9 fused vertebrae in the sacrum and the coccyx.
ADA Clear Doorway widths. Two doors in series must have a minimum of 48â in addition to the width of the door(s) swinging into the space (so a 36â door swinging into a hall would require the hall to be a minimum of 7â-0â long before any other door could be placed, if the second door does not also swing into the hall).
Quick Answer. The maximum interior height of an entry door threshold is 1/2 inch, and up to 3/4 inch on exterior siding doors where it is essential to keep water out, as stated by the United States Access Board. These height limits improve wheelchair access to buildings.