A highly efficient, simplified method and apparatus for joining knitted shirt sleeves to shoulder openings of knitted shirt bodies. A knitted sleeve section, oriented outside-out, is engaged by a limited shoulder edge margin only by guide rollers, which can be separated to apply a very limited, controlled circumferential tension to the mounted sleeve section. A knitted shirt body, oriented inside-out, is positioned with a shoulder edge margin directly surrounding the shoulder edge margin of the sleeve section, and also maintained under light tension. A retractable support is positioned underneath the free portion of the sleeve section during loading of the shirt body. The two fabric sections are arranged to be controllably advanced in unison by the guide rollers on which they are supported while a sewing operation is performed. Immediately in advance of the sewing station, the respective shoulder margins are separated by an intervening plate and are individually engaged by active edge guide devices operating in response to a novel arrangement of individual fabric edge positioning sensors for the respective shoulder margins. Immediately in advance of the active edge guides, decurler devices are provided to flatten and extend the edges of the shoulder margins, assuring that the subsequent edge alignment and sewing operations can be accomplished with a high level of accuracy and reliability.