5:51 i know this years late but wat they mean by 1/2 inch x 2inch on each side of spacer blocks is the construction of the ribs if u look at the other side of the diagram it tells u about the spacer blocks being 2 x 4 x6 1 strip on each side creating the rib or truss
It really shows that you did not build this greenhouse, " I dont know what 1/2 x 2 spacer means" it's not a spacer its support strips to make the structure ridged. You really are taking credit for someone else building the greenhouse in your prior video.