Each horizontal frame is composed of six pieces. The front and back are connected by braces, forming sort of a Roman numeral II (or a thick ‘H’). Side braces complete the frame but aren’t directly connected to the H-assemblies. (They’re indirectly connected via the rack’s overall framing, and by the shelf panels, but not until later.)

It’s critical that the parts forming the H-assemblies are flat (planar). To build them, I formed a jig by clamping some 2x4s (cauls I use for panel glue-ups) to my workbench. I clamped the back of the shelf to the bench upside-down, then used a spacer to position the interior braces, which I then screwed into the back.

To complete the assembly, I clamped the front of the shelf to the bench and rotated the sub-assembly 180 degrees and screwed the other ends of the interior braces to it.

As an aside, in Matthew Peech’s build video, he suggests drilling pocket holes in 2x2 braces in different sides on each end (say, on the top on one end, and on the side at the other) to keep the brace from rotating. I tried that, and it didn’t work for me. The pocket screw exited the brace in/close to the center, so the brace rotated anyway. To prevent that, I used two closely spaced pocket holes in each brace (which dramatically increased the number of screws I needed).

I mentioned earlier that I didn’t pre-plan the locations of the pocket screws, opting to figure it out during construction. Here’s one pitfall of that approach. I thought I’d use pocket screws on the inside surfaces of the side braces to attach them to the rack’s outer frame. That would have worked, unless I added the interior bracing first, which is exactly what I was doing. With the braces in place, there’s no way to drive the screws. Therefore, this shelf bears a scar of shame—two pairs of useless pocket holes. The finished rack has other scars too—unused pocket holes that seemed like they would work but didn’t because there was no way to get a screw and driver in place. That’s okay for shop projects like this, but it wouldn’t be for a real piece of furniture.

I built all the H-assemblies, then attached them to the rack’s main frame. Getting them positioned was a fussy process. My SketchUp model shows some side frame lengths measured in 64ths of an inch. There’s no way, at least for me, to cut braces that precisely, so I got as close as I could. If I cut a shelf’s braces too short, the shelf would sit slightly higher than designed. If I cut them too long, the shelf would sit slightly lower. In the end, I marked the theoretical positions of the frames, then dry fit the H-assemblies and tweaked their positions until (1) they stayed level, and (2) their fronts and backs aligned with the main frame. Then I clamped them and drove the screws.

The next step was adding the side braces. I used a straight edge to align them with the installed H-assemblies, then clamped them and drove the screws. Clamping was easier said than done, because the clamps and braces tended to shift because of the angled front surfaces.

I eventually got them all in place, and the rack’s skeleton was complete. I couldn’t use pocket screws to attach that very narrow shelf top-most shelf. The pocket holes are there, but I couldn’t get anything in there to drive them, not even my stubby screwdriver with a short bit. (A right-angle drill adapter probably would have worked, but I don’t have one.) I had to use a screw through the outer frame into the ends of the braces to attach them. More scars of shame.

It was nice seeing the rack’s skeleton complete. I could even use it to store the half-width hardboard panels. (I had them cut in half lengthwise at Home Depot so I could fit them in my Honda Element.)