Okay, its not really a thread, but it may as well be. These truss systems are popular for overhangs and porches on commercial and residential buildings. Typically, the top end will sit on a nailed 2×4 or rest on the top of the wall and toenailed into the joist for I-joist.
These are very danagerous and will fail easily under fire conditions. Always take a look above you before you enter the building of any type.
On another note about these overhangs, canopies and porches; when using search lines, make sure you tie off outside the building which inlcudes these overhangs, canopies and porches. Get outside of these areas and into an open area free from any building components. As always, stay safe and be careful.