At the indoor climbing place I go to there is a big vertical board with lots of circular holes arranged in a grid, you hang on 2 'pegs' that slot into the holes, and you have to pull one out, and put it in a higher slot.
At the indoor climbing place I go to there is a big vertical board with lots of circular holes arranged in a grid, you hang on 2 'pegs' that slot into the holes, and you have to pull one out, and put it in a higher slot.