Reply by HokieKen

If you go in person to buy your square, you can check it in the store using a pencil and the flat edge of a shelf. Just keep trying different ones until you get one that works. Also, combination squares can be trued up with a piece of sandpaper: http://www.instructables.com/id/How-to-square-a-combination-square/
I have and like one of the PEC combination squares but if you re willing to fiddle you can tune up a cheaper one.

- jdh122

Indeed, it’s not hard to true a cheap square (assuming the blade is straight). But, beware of the Aluminum ones – they won’t stay true long because of the wear between the head and the blade.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA