The solar collector is a salvaged metal roof that was spray-painted dark green. All you graffiti artists likely know about the handle sold by Rustoleum but it makes spray painting much easier.
Speaking of graffiti, I have been very impressed with the work of Banksy; almost seemed like a precursor to the London riots.
I cut the metal panels to length using a metal cutting wheel on a 4.5 in grinder with lots of sparks. Wear your safety glasses...always.
I installed a wooden lip on the back wall to support the top of the metal panels and created a 2 inch by 4 inch "shelf" with a back stop to support the base of the metal panels. The metal panels rests on these shelves and can be removed if need be.
I left a 8 inch gap between the panels and the front wall for air flow.