If you look at the back of an upright piano, you will see a large thin wooden panel that comprises most of the back of the piano. This will have diagonal slats (ribs) glued to it. If you tap on this with your finger, you will notice the amplification of sound that this creates. On a grand piano, you can find the soundboard inside, under the strings, and often with a decal bearing the piano's maker. Underneath, the grand will look much like the back of an upright. Soundboards of some cheaper pianos are laminated (like plywood) and claim they will never crack. The best soundboards are tight grained spruce panels from old growth trees that produce the highest quality tone amplification.