This is also very important information if you want custom arrows which group tightly. You have three choices:
No shelf - typical of a horse bow and some longbows and stick bows.
Center cut shelf - This is the shelf you nearly always see on a wooden longbow or recurve bow. (see photo below. You can see that the shelf still puts the arrow on the side of the bow, not in the middle of the bow as a center shot bow shelf.
Center shot shelf - This is what you nearly always see on compound bows. We all know what those look like, right?