The mission was to create a thing that would allow 2 bins to be taken down this narrow space by one person, in one trip.
Step 1: Pattern
To make the pattern, I cut out a piece of scrap cardboard the same size and the wood I planned on using (scrap 2x4)
With the cardboard cutout lined up with the bin lid, I drew a rough line with the pencil running along the lid.
I then added the rounded end and the hook shape which would go under the handles of the bin.
Once that was done, I cut out the pattern and tested how it fit, it need a few tweaks to make sure the wood was clear of the lid and the weight of the 2nd bin would be transferred to the front lip of the smaller bin rathe than the lid.
Once the cardboard fit well, I transferred the outline onto two 2x4s.
Step 2: Drilling and Cutting
Before cutting out the shape, I drilled 22mm holes on the ends (I already had 22mm dowel on hand), you could use whatever size you deem strong enough).
Then, cut out the shape on the bandsaw.
Note: When doing this try to keep the long cutout piece as intact as possible as they will become the cross braces. The bulge on the lid is about 260mm across so I cut the cross braces to 270mm to ensure they fit around.
Step 3: Putting It All Together
I lost the photos of me doing the doweling, but suffice to say, I used 8mm dowel and wood glue to put everything together.
The 22mm dowel sections used for the lifting were cut to size based on the clearance between the smaller bin and the underside of the handles of the bigger bin.
Glue, clamp up and leave to dry.
Step 4: All Done
To use the Shifter, drop the hooks in under the bin handles and lower onto the lid.
Push the smaller bin up under the larger and tilt back.
Now, because I didn't really expect this to be successful, I used timber from an old bed frame. In hindsight, I really should have made it from H3 or some other treated timber so it could be stored outside with the bins.
For now, I'll just have to paint it.