Because heated gases tend to rise, the trapped gases flow within the confines of each channel until the channel is filled and then spill around the lower edges thereof into the open spaces between channels in a manner that helps distribute both the heat and flavoring {HEAD ~ vapors} evenly over {TAIL ~ the entire cooking surface} of the grill 
evenly over
Because heated gases tend to rise , the trapped gases flow within the confines of each channel until the channel is filled and then spill around the lower edges thereof into the open spaces between channels in a manner that helps distribute both the heat and flavoring { HEAD ~ vapors } evenly over { TAIL ~ the entire cooking surface } of the grill
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