Finally I decided to turn the entire unit upside down to get a better look at forcing the side down over the rectangular peg - the one towards the back corner

This thing is incredibly cheap looking

And finally, the whole thing just has a very cheap look to it

It's strong (capable of holding 100 pounds on each shelf) and will help tidy up any shop or garage by providing a good looking cabinet in which to store power tools or supplies like paint.

Once assembled it's a nice-looking unit, and has a fair amount of storage for garage odds and ends as well as a sturdy top to hold larger items

I paused the YouTube video as I went along as well as looking at the instruction sheet