This is the main assembly stage of the production process, where sewers stitch fabric pieces together, and a garment is assembled. Computerized sewing machines (costly), can be programmed to sew a specific number of stitches to perform a standard operation, such as setting a zipper or sewing a collar.

However, even though new machines mechanize and hasten the sewing process, sewing remains largely labor-intensive. There are four general types of sewing machines: single-needle machines, overlock machines, blind-stitch machines, and specialized machines. Single needle machines are most common, as are their operators. Because operating more complicated machines requires additional training, there is frequently an oversupply of single-needle operators and a shortage of sewers who can use other machines.

Sewers need to be familiar with many different types of fabric and how to stitch each, but they usually specialize in a particular fabric or a particular machine. Working with cotton knit fabrics is very different from working with denim, silk, or linen. Learning how to work with each fabric type is part of the training-usually informal-that sewers undergo. Sewers may also specialize in zipper-setting, embroidery, and other hand stitching techniques.

Sewers may also affix labels. Certain labels identify the garment as belonging to a particular line and designer. Other labels inform the consumer of fabric content, care instructions, country of origin, size, or production by a union shop.