This square of woven rug or heavy cloth is about two feet on a side but folds up to fit in a pocket. Such cloths are popular with second-story thieves, and those who live or die by running from rooftop to rooftop in big cities.
As an action, you can unfold the cloth and place it so that at least one edge touches a solid object, such as the edge of a building or a cliff. It remains perfectly horizontal, supporting up to 400 lb., for up to 10 minutes. You can cause it to release early by touching it with your hand and saying the command word. The rook-perch can be used once in this way and recharges at dusk.