This work by Andrew Schoultz and Aaron Noble has inhabited an outdoor San Francisco wall for more than six years and seems to be holding up well. It occupies the side wall of a vintage store called The Apartment on the corner of 18th Street and Lexington. Lexington is a little street parallel to Valencia between Valencia and Mission. Quite a large example here of the "boy-cartoonist" style, full of force and motion and machinery. My favorite is the bottom picture where two actual brass pipe-fittings are coaxed into collaboration with a mysterious trompe-l'oeil piece of gadgetry.