Gathering is needed to shorten a section of fabric to make it fit. Use large stitches to make a machine-stitched line on either side of the marked seam line, then secure one end of the threads by wrapping them around a pin inserted across the stitching line; pull the under-thread to reduce the fabric to the required length, spreading out the gathers equally. When later joining the seam, work from the gathered side on top of the flat fabric so that you can ensure that the gathers will remain spread out equally. Remove the visible line of gathering from beside the finished seam. If you have a long piece of fabric to gather, divide it into shorter sections and gather each separately.