Slide the Pre-Loaded Inside Corner Bracket along a 15mm Extrusion - 225mm just far enough, so that the corner of the bracket is flush with the end of the Extrusions. Tighten the Nylock Nuts until snug.
Add another Pre-Loaded Inside Corner Bracket to the opposing side of the Extrusion from the other Inside Corner Bracket. Tighten the Nylock Nuts until snug.
Internal Cross Member Assembly Complete
Repeat the step above until you have four complete Internal Cross Member Assemblies.
Internal Chassis Frame Assembly
Slide an Internal Cross Member between two 15mm Extrusion - 420mm until the Cross Member sits roughly towards the middle of the Extrusions. Tighten the Nylock Nuts on the Brackets until snug.
Slide another Internal Cross Member Assembly along the 15mm Extrusion - 420mm, until the end of the Cross Member Extrusion is flush with the ends of the assembly. Tighten the Nylock Nuts until snug.
On the opposite side of the Internal Chassis Frame from the previous two Cross Members, add another Cross Member to the assembly. Slide the Cross Member towards the middle of the two 15mm Extrusion - 420mm. Tighten the Nylock Nuts until snug.