2x Hidden three-way corner assembly from the last step

1x T-Slot extrusion 3030 - 160mm

Ensure the extrusions are flush and square with the hidden three way corner assembly before and after tightening the screws.

Tighten the M6x8 set screws.

Be careful while tightening the set screws, extreme force may break the three way hidden corner.

Prepare two assemblies

2x T-Slot extrusion 3030 - 400mm

Assemble the parts as shown.