Steve , I've spent a good number of hours with a screw driver in hand and tuning calls. Its all part of making the call your using to sound as proper as possible. Sand paper is the same and how it is cleaned. As some don't use a corse grit, I can a sure you that I do have some heavy duty sand paper and I use it every now and then and it can make a bad box sound good.

Next time we get togeather I can show you the proper way to tune a box call...