Edges can be extruded to create new polygons. Edges are extruded with different behaviors depending on whether they are ‘internal’ or ‘external’ (inside the mesh, or on the perimeter boundary). The constraint methods are the same as with extruding polygons, so only issues specific to edge extrusions are shown below. Tools are organized into tool groups. Each tool within the tool group can have its own key, but can be cycled to via a ‘tool group’ key. By default, the U key cycles the tool group, but also activates the current tool within the group when another tool is currently