Bill Tindall, E.Tn.
Well, actually table on desk but it looks like desk on desk.
Finally got the myriad of joinery and other necessities done on the parts and glued it up. 18 joints come together at once. I always glue up a case all at once so I can ensure everything comes together as planned and adjust the whole assembly as needed.
If a case comes up square it makes fitting drawers much easier. Hence, I spare no effort in getting the dovetails and M&T right. Juiced up the sliding joints with liquid hide and slide the parts together. Squooze it tight with clamps and checked diagonals. It's on the desk because the desk is a reliable flat surface. (my bench has had a hump in it for decades. I'm waiting for David to visit and flatten it. In the mean time it's the desk for glue ups)
When checking for square a square can be misleading. If one of the parts is even slightly bowed squaring with square will drive one bats trying to figure why a side if off one way and when measure on the opposite side it seem off another.
Measuring diagonals is the way to go. So how did it do? 13061 mm by 13060.5. Good enough.