What is the primary function of a foot pedal in sewing?

The primary function of a foot pedal in sewing is to control the sewing instrument's needle movement. When the foot pedal is pressed, it sends a signal to the sewing machine to begin stitching, typically causing the needle to move up and down in a rhythmic motion. This allows the sewer to have hands-free control over the sewing process, providing the ability to adjust the speed of stitching based on the pressure applied to the pedal. This feature enhances the ease and precision of sewing, enabling better control over the fabric being stitched.

The other options do not accurately describe the primary function of a foot pedal. Measuring fabric is the purpose of different tools like measuring tapes or rulers, automatic threading involves other mechanisms within the machine, and adjusting tension relates to separate machine settings rather than the foot pedal function.