An electric heater assembly (16) adaptable for battery operation with hand held devices for attaching, sealing or shrinking heat activated plastic or mylar film materials includes a heating element (20) comprising a planar electrically insulating substrate (18) having a heating element (20) being a thick film conductor delineated and fired on one of its planar surfaces in a configuration that realizes local high power density in the heating element and the resultant production of localized high heat energy within the substrate with minimized power consumption from an external electrical source. Enclosing the heater assembly is a sheet metal sheath (24) to provide mechanical protection and to effect heat transfer to a work. The heater assembly is positioned, with the heating element facing up, inside the sheath with its opposing surface atop of, and in intimate contact with, a planar base (24a) of the sheath, a workface (26) comprising an opposing side of the base.