I’ve seen people in a gym ‘working out’ using a system consisting of a central rail with moving handholds and footpegs on the outside.
Today’s invention (didn’t find it in a search of the patents) is a variant on this which works as a ladder.
As shown, a person would place their feet in the stirrups and hold the handles. Both stirrups and handles would be free to slide up in slots on the inside of each of the risers.
When any downward pressure was applied to either, a simple ratchet would stop any downwards movement.
This would allow someone to climb the ladder conveniently, using steps with a variable size.