I am confused as well. I can't think of any place to put a "silicone gasket" on a grill. The only thing I can think of is how they run a line of the Red Permatex gasket material along the underside edge of the end caps between them and the hood to prevent gas/heat leakage. Regular silicone will simply burn up is used anywhere near the cook box.
I think we need a more detailed description or pictures of exactly what you are asking about Ryan.