Firefighter training stairs.
https://s3-us-west-1.amazonaws.com/h...s_fullsize.jpg
Previously:
https://www.homemadetools.net/forum/...714#post206132
https://www.homemadetools.net/forum/...272#post142022
https://www.homemadetools.net/forum/...532#post185732
https://www.homemadetools.net/forum/...403#post161954
https://www.homemadetools.net/forum/...382#post150757