I have decided to break down and buy a quality square, as my cheap big-box combination square, which seemed close enough when I bought it, has gotten out of alignment, which I assume was wear on the sliding mechanism. My primary needs are a simple, reliable 90 degree square angle and I want something longer than a 6" try square. I've narrowed my choices to the Starrett C11h-12-4r and the Woodpeckers 1281, as both have a good reputation for quality & squareness, both have clear and accurate measurements, and both are about the same price.
I lean toward the 1281 because I do not need the flexibility of a combination square (90 degrees reliability is 99.9% of my intended purpose) and Woodpeckers offers a lifetime guarantee for squareness. However, I waffle on my decision since the Starrett is steel versus the 1281's aluminum construction, and I know the square will drop on the concrete someday. On the other hand, I worry about wear on the sliding mechanism of the Starrett causing it to lose squareness in time, and I've been told it is very expensive to recalibrate.
Any thoughts appreciated that would push me over the top either way.