I'm sure this is a very elementary question. I bought some chips and the metal box to house them. Unfortunately, the box contains no instructions as to where to put them. I have a 3 burner Weber grill and will be cooking ribs indirectly. So, which burner do I place it by? And, more importantly, where do I place it (i.e. over the grate, under the grate on the flavorizer bar)? Thanks for your help.