The viewing hole is of {HEAD ~ a predetermined size} so as to preclude convection flow sufficient to cook food, whereby the food will cook by {TAIL ~ radiant heat} only 
The viewing hole is of { HEAD ~ a predetermined size } so as to preclude convection flow sufficient to cook food , whereby the food will cook by { TAIL ~ radiant heat } only
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH