I remember working on an old farmyard barn roof as a young labourer using a cat ladder, on me tod.
I got up the upright ladder and onto the cat and worked on the roof replacing the odd plain tile.
Rather than move the upright set of ladders to reach a tile just a meter the other side, I stood on the ridge and hoiked the cat over the upright ladder so I could reach.
Only problem was the old barn roof had a crown on it. As I descended, the cat ladder settled and the hook came off the ridge. I was fortunate that the upright ladder was still within reach of my foot. Only trouble was I didn't tie it back.
Me, the cat ladder and the upright ladder slid away from the building until I'm doing a rather elegant 'splits'. Luckily a farm labourer saw my predicament and climbed the ladder so that his weight pushed us back to safety.
Looking from the ground afterwards you could see that one part of the roof was ancient and bowed and the more recent part was straight.
Great fun the early 80's. I gave my Clima cat ladders away 10 years ago.