Quote Originally Posted by jdurand View Post
Bet it leaves two nice dents in the roof, especially on a warm day.

It would be good to take a board with you to put under the clips.
Agreed it could impact on a felt roof but only if the ladder is footed on soft ground in which case a plank would be better of at the foot of the ladder. It is meant to be a stabilising attachment not load bearing. Shouldn't be too hard to make something similar if so desired.