Here's my theory:
1. The person in the chains has to bend knees and lower down to get out of the chain 'cage', use hands to hold the lower chain rings so that they don't get in the way.
2. Both people switch places - the first person holds the chain rings so that the other person can easily "put them on"; sleigh into the chain 'cage' from the bottom 'opening'.
3. The other person has to stand up to 'enter' the chain 'cage'
So basically its get down -> switch places -> stand up rountie.
It's alos possible that the pole can be in a way 'opened', as the chains are connected to opposite sides of the pole, so that the chain 'cage' is open and people can switch places, then close the pole like doors behind them.