This is the building sketch from last years lower frame. The connector pieces were simplified because our machining capabilities were more limited last year. This year we have the machine shop teacher as one of our sponsors and his best students are lined up and excited about making parts for us so we can make connectors more like the quick frame pieces (wow that's a long sentence.)
You can see how we notched some of the pieces (kind of like Lincoln Logs) for assembly. We had more of these on the upper frame than the lower frame. These were hand fit and very strong when glued.
The holes you see are for 1/2" aluminum rod that connected the upper and lower frames together. Pictures I will take Monday will show this better. This may also change with our new machining capabilities.