I learnt some things while I was undertaking some very rough cabinetry.

1. My square, at least my "second biggest" square isn't. I've checked it before but I guess it's had a knock because it is now about 3mm out over a 400mm blade.

2. My cordless stanley saw, which I used to like, is able to cut a taper while using a guide. So much flex that a 500 wide cut ended up 6mm out of square.

Fortunately I noticed the 3 shelves were different sizes and shapes before I attempted to screw it together in a very tight space...