What does "rap" mean for brownies recipe? I just made Ina Garten's Outrageous Brownies last weekend and I omitted the "rap" step: "Bake for 20 minutes, then rap the baking sheet against the oven shelf to force the air to escape from between the pan and the brownie dough."

What did they want me to do, push the pan against the back of the oven? Thanks.
The oven shelf is not the back of the oven. Basically what you would do is lift one side a little (maybe an inch or so) and let it drop. Then you can do the other side. This will give you a more fudgy and less cake-like crumb, as the cake-like finish comes from trapped air bubbles. If you rap the pan to help the air escape then you have less trapped air and thus a denser, more fudge-like crumb.