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).
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.