PianoShop.co.uk :: Info :: Figures :: Piano Picture Gallery
This page shows the difference between Straighstrung and Overstrung upright pianos.
This is a picture of a straightstrung upright piano with the front taken off and the action removed. See how all the strings are vertical.
This is a straightstrung piano seen from the bottom:
This is an overstrung with the front taken off and the action in place.
The action is an underdamper action. (The dampers cannot be seen here, other than the leftmost two, below the hammers).