Edges are primarily used to designate room sides that connect to wall flaps.
By default, edges are rendered as orange lines. The type of line indicates the fold direction of any attached flaps:
When a wall flap is attached to a room, an edge line between the floor and the flap is automatically generated. Certain properties of the attached flap and the edge itself can be modified by selecting the edge and double-clicking it. Doing this brings up the Edit Edge window.
Edit Edge Window
3. Edge Product
Tip: Select a room, then double-click a handle on one of its sides to open the "Edit Edge" window and select a product. Using Edges in this way can be a simple method for assigning bullnose tile or similar products.