This is the bit where you need to be sure everything fits perfectly (well, as perfectly as your preferences tolerate)
You also need to take it apart to glue. For this reason, you also need to mark how each part connects to the others or you'll glue the wrong bits together.
Here's the base...
This is being clamped together after gluing...
Before gluing all the joints were trimmed to make the mitres fit as snugly as possible. Then the farne was rechecked to make sure the corners were stil square. They were!
So, as the joints were snug and square, the whole thing was taken apart to glue it. You can't really see it here, but each base board and all four rails are numbered so it is easy to see where they fit together.
The boards are pretty rigid (they are blockboard library shelves), but to make the base really solid and hold together, I fitted two 10mm dowels between each butt joint so the planks would form one big board when glued and be super strong.
The router makes a great clean hole and its guide rail and depth guide mean they are all consistent.
This is all that is holding that together. the dowels fit snugly, so they are tight.
You can see one of the numbers used to ensure the disassembled boards went back in the right order later. Here, I am testing they all fit.
The numbers 3 and 4 are clear here.
For extra strength, I roughed up the grain on the end of the planks, so the glue would have something to bind into. I used a riffler (rough sculptors rasp) for this.
The plank rebates being glued into the four mitred edge rails.
Finally the whole lot was glued up and put together, then clamped.
To start with 2 sash cramps were fixed across each short rail. The tenons were on the end of these rails and the cramps held tenons firmly into the mortices in the long rails.
Clamping can shift the angles, but the joints turned out to be pretty square. The angles were still dead square. Quiet mental pats on my back.
But it is not just shear that can affect the integrity of the joint. They can also be slightly twisted so the edges don't line up. For this reason the corners were clamped with wooden planks to keep the mitre edges aligned horizontal while the glue set.
I used whatever plank pieces were lying around.
To prevent twisting, I put the whole thing on the floor, which was the largest flat area available.
This was left for about 36 hours...