If you didn’t leave a HTJ5 self-tapping screw to the end of the back extrusion bar earlier, screw one back in, a few mm’s short of fully inserting it. Take the 140mm 20×20 extrusion with three holes trough it, and slide it to the bracket extrusion nuts and then to the head of the screw as shown. Note the hole orientations!
Tighten first the self-tapping screw through the hole in the shorter extrusion. Make sure the mount is square and the bottom is flush. Secure the joint by tightening the thick bracket in to place.
Hint: This stage is easiest to get square by laying the bars flat on the table.
- 140mm extrusion with three holes
- HTJ5 self-tapping screw