Which type of stitch is primarily used for permanently joining pieces of fabric?

The straight stitch is primarily used for permanently joining pieces of fabric due to its straightforward and secure nature. This stitch is made by creating a continuous line of stitching that penetrates the fabric, resulting in a strong seam. It is commonly used in most sewing projects, including garment construction and home furnishings, because it provides durability and a clean finish.

In various sewing applications, the straight stitch can handle different fabric types and weights, making it versatile. It is also the foundational stitch in sewing, from which other techniques and stitches are developed. Its ability to create a reliable seam makes it the standard choice for basic sewing tasks.