Sewing pins help hold two pieces of fabric together and prevent shifting during machine sewing. Seamstresses and hobby sewing enthusiasts each have their own methods for pinning fabric, and each individual will expound on the benefits of their method. Some insert pins parallel to the hemline or seam, while others insert them perpendicular to the hemline. Either method is acceptable, provided the pins do not come in contact with the sewing machine needle.
How a particular sewing pin is inserted does not matter as much as how the fabric is lined up and how close together the pins are along the hemline. Placing pins too close together can slow down sewing and create fabric bunching. Pins placed too far apart allow for gaps and fabric shifting, as well as bunching and misaligned seams. Seams should be aligned carefully and pinned to ensure an adequate seam allowance of at least 1/8 of an inch (3.175 mm.)
Exact placement of sewing pins determines if the pins must be removed prior to stitching. Traditionally, most seamstresses pin hemlines at the edge of the seam allowance, approximately centered where the sewing needle will travel. When sewing pins are inserted at the fabric edge like this, they must be removed as they near the machine's needle. If inserted perpendicular to the hemline, keeping pin heads outside the fabric edge allows for easy removal during sewing. For sewing pins placed parallel to the hemline, the direction of the pin head is up to the user.
Although placing sewing pins near the fabric edge is common, pinning the fabric a finger width or more away from the hemline is also common. This method does not require removing pins as the user sews, because the sewing pins are outside of the direct path of the sewing needle. While this can speed up sewing time since the pins remain in place, it does not provide a smooth, flat seam and can cause slippage or bunching. Extra care is needed to keep fabric edges properly aligned if sewing pins are placed too far away from seams.
Any method of pinning fabric that works for a particular individual's sewing style is acceptable. Factors to consider when selecting methods for inserting sewing pins include the type of stitch used and working with pinned fabric. Sharp pin points can easily prick skin, snag stray fabric, and scratch work surfaces. Needle points should be kept away from fabric edges and lay flat against the fabric. Various types of sewing pins are available, with a variety of lengths and pin head types, which should bare consideration.