3 ply is generally used in normal construction, it consists of thin upper and lower veneers with a thick core not really the proper thing for delicate S/S work. BB has many layers of veneer, depending on the thickness, all of the same high quality, and therefore stronger and less likely to fall apart on fine cuts. Most people use it because it is made of beech or birch and is white in colour making it easy to stain to anything you want. Having said that, you can use any good quality ply such as marine ply as they are built to the same high specs but are generally darker and therefore less easy to stain. Hope this helps. Iggy