Select > Convert Selection > To Contained Edges
 
 
 

Changes the current selection to any polygon edges that can be selected depending on what components were originally selected.

For example, if you have a polygon mesh comprised of four-sided polygons (quads) with several vertices selected and then choose Select > Convert Selection > To Contained Edges, only the edges that have two selected vertices are selected.

Tip

Many of the convert selection features are available from the context sensitive polygon marking menu when you press + whenever a polygon component is selected.