How a house is built
Triangles in the roof
A truss is a frame of triangles. The members stay in tension or compression when the joints are left intact.
Arrow keys turn the house. Plus and minus, or the zoom buttons, change the zoom. A horizontal drag turns it after you tap the drawing. Reset view returns to the step camera.
The drawing needs WebGL. The notes on the page still stand.
A truss spans with less depth of solid wood by folding the shape into triangles. The top chords follow the roof, the bottom chord ties the walls, and the webs fill the middle. Each member is sized for tension or compression. The joint is part of that design.
Cutting a web, or notching a chord, breaks the triangle. Storage and ducts have to fit the openings the truss was designed to have, not holes made later. This house is drawn as roof planes. Those planes could be trusses or rafters. The drawing does not choose.