For the people who say those 90Β° angles aren't accurate, I just have to ask, what tool did you use to check them? I went all out and ordered 8 (4 pairs) of these tools almost at the same time as ordering Woodpecker tools. As you can see I checked the inside and outside for squareness. And unless all of my woodpecker tools are broken (highly unlikely isn't it) which is this 851, each of the corner clamp squares are at the top for accuracy. And I mean EXACTLY! I even held each of them up to a bright light, and not a single ray or streak of light passed through any part of the rim; inside or outside.