For seaming fabrics together, at least two fabrics are arranged on the working plane (3) of a sewing machine (1) with their edges against each other. The fabric edge strips are aligned downwards at right angles and the edges are cut, and the separate edge strips are folded under the first fabric. The material is stitched along the line of the folded material to give a stable bonding. Also claimed is a sewing machine assembly with a straight guide slit (19) in the working plane (3) parallel to the stitching direction to hold the downwards edge strip of the fabric. The slit (19) extends from an outlet opening (19b) in front of the main presser foot, in the direction of fabric advance. A cutter (22) acts in the slit (19) below the working plane (3) to trim the edge of the downwards fabric edge strip. An auxiliary fabric advance (28) is at the working plane (3), near the slit (19) in front of the cutter (22), to act with the main advance grip (6), to move the fabric according to the tension and/or push forces applied in the stitching direction. USE/ADVANTAGE - The method is for seaming fabric sections together, such as in garment making. The operation seams materials together without preliminary overcast stitching to prevent edge fraying.