Module select 

Walks over a cage’s edges, for selecting and for the edits that follow them: the ring across the quads either side of an edge, the loop straight on through its vertices, and the boundary run of an open cage.

Structs

Ring

The edge ring of an edge: the edges reached from it by crossing quads to their opposite side, until the ring closes, or meets the cage’s boundary or a face that is not a quad on both ends.