A "roofshooter" pagewidth printhead for use in a thermal ink jet printing device is fabricated by forming a plurality of subunits, each being produced by bonding a heater substrate having an architecture including an array of heater elements and an etched ink feed slot to a secondary substrate having a series of spaced feed hole openings to form a combined substrate in which said series of spaced feed hole openings communicates with said ink feed slot, and dicing said combined substrates through said ink feed slot to form a subunit. An array of butted subunits having a length equal to one pagewidth is formed by butting one of said subunits against an adjacent subunit. The array of butted subunits is bonded to a pagewidth support substrate. The secondary substrate provides an integral support structure for maintaining the alignment of the heater plate which, if diced through the feed hole without the secondary substrate, would separate into individual pieces, thereby complicating the alignment and assembly process.