I bought two Irwin combination squares - 12" and 6". Both squares are of the same construction with heavy duty 90* and 45* machined cast zinc handles, knurled brass locknut, marker awl and level cap. Scales of 8", 1/16", 1/32" and centimeters/millimeters. A simple but effective squares test is to mark the 90* line, then flip the square and place the line over the previous line to mark. Any discrepancy in the lines would indicate that the tool is not square. I was happy to see that both squares passed this test when I took them out of the box. I realized they were junk. by some ) Irwin Squares I am VERY pleased as these Irwin squares are heavy, precise, with great finishes and workmanship, and are made from materials that will handle all weather conditions, I would happily spend twice as much for tools of this quality.