I have been making furniture as a hobby for some years now and I discovered very early that practically ALL woodworking tools came as a project, not as a finished product.  That is to say that most tools need to be sharpened or adjusted or tuned,etc.  Starrett tools are the exception, my square came out of the box perfectly square and functioning flawlessly.  That is the very reason why I purchased this tool.  I use it to adjust and tune and square all those OTHER tools!  Every serious shop needs a few very good reference tools, this is one.