The guitar top is actually two panels stuck together

Take a close look and you should notice that the wood grain on the guitar top is symmetrical. This is also true for the back and sides, because guitars should ideally use the same material in order to transmit sound evenly. Two planks are taken from the same location in the trunk and-like an open book-the planks are lined up horizontally and attached. This is particularly true for the top and back, where the parts of the wood where the growth rings are most concentrated (i.e. toward the outside of the trunk) are brought together toward the center of the instrument. This is called "bookmatching."