<HTML>  Phil      I have'nt measured a piano yet that had a belly rail and spine(straight side) at 90 degrees.The Stwy B is something like 93 degrees or so. Most pianos measure 40 or 45 Degrees of the spine. Usually one or the other .To me it's just less numbers to remember.  The lower the number  of degrees (40 or less) the longer  the long grain is in the panel.  Dale</HTML>