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