Shape descriptors and feature-based representations are of primary interests in the area of solid modeling. They allow us for easier storage, recognition and general treatments of objects. Axial structures such as skeletons are popular shape descriptors which have been widely studied. Most of the studies focus on a particular type of skeleton called the Medial Axis. Medial Axes can be extracted from discrete volumetric data as well as boundary-based representations. In the later case, however, no algorithm is known to perform well and accurately. We propose a new paradigm for constructing one dimensional axial structures associated with a polyhedral object. These structures, called the level set diagrams, are associated with scalar functions defined over the set of vertices of a polyhedron. We study in details the level set diagram associated with the shortest path distance to a source point. This particular association fits nicely into a theoretical framework and presents interesting properties for the purpose of shape description.