blend in quickly with the primary flame the periphery of the insert 20 contains a plurality of edge openings or notches 32 the bottom of each notch 32 is stepped to form a throat 33 downstream from each throat 33 each notch 32 is deeper thus 1 forming an expansion region 34 tertiary flames are produced by the burning of the portion of gas air mixture which exits the notches 32 the tertiary flames are very short and burn close to the burner face 23 forming an outer mantle of flame hhich quickly blends in with the secondary flames the tertiary flames keep the gas air mixture burning close to the burner face thereby preventing lift off the flame retention insert 20 is held in place within the burner head 13 by two dimples 35 one is shown in fig1 the dimples 35 are located on opposite sides of the burner head and interact with a corresponding bottom of a notch 32 the burner nozzle 10 is made by stamping two virtually identical halves 38 39 out of aluminized steel the second half 39 has lips 40 at its outer edges which are folded over outer edges of the first half 38 to form the nozzle 10 the nozzle therefore has two diametrically opposed double walled flanges 21 which define the plenum chambers 22 since a burner nozzle is typically used.