I'm in the middle of deconstructing a failed attempt to make a solar air heater panel...the panel was supported by some 2x4 uprights constructed with some 10x100 dominos. It was a quick and dirty construction and now that I'm decommissioning it we thought we'd try and break it by loading the joint (standing and jumping on it)
 
My son stands on the horizontal strut

Adding his girlfriend and it still holds

I was amazed that the joint did not give, even with a foot long lever. I cut open the joint with the bandsaw so you can see how simple the construction. Very cool.