Open Tread

This stair is under construction. Two of the components are in place: stringers and risers. The treads are not in place. In the foreground you can see the concept of an open tread.  The stringer is cut in a rise  (vertical) and run (horizontal) pattern, creating a saw tooth look.  
This open tread stairs will have a support wall under the stringer.  The background stringer is a closed tread stringer and will also have a support wall.  
Rail and balusters are placed on top of the tread end creating a typical open tread stair.