 In this way, the straight skeleton can be used as the set of ridge lines of a building roof, based on walls in the form of the initial polygon.The bottom figure in the illustration depicts a surface formed from the straight skeleton in this way.Demaine, Demaine and Lubiw used the straight skeleton as part of a technique for folding a sheet of paper so that a given polygon can be cut from it with a single straight cut (the fold-and-cut theorem), and related origami design problems.