Why You Should Use a Leader and Ender Strip When You Sew
When machine-sewing together pieces of fabric, stitches should appear on both sides of the fabric without loops, surface knots, or broken threads. If your threads are becoming a tangled mess, try using a leader and ender strip.
Without much fabric for your machine's feed dogs to grab, the first few stitches can be swallowed into the machine's throat plate. Work out the kinks before you start piecing by first sewing across a fabric scrap, sometimes known as the leader or ender (see green rectangle in picture).
Chain-piece by feeding subsequent pieces under the machine needle without lifting the presser foot. Trim off the starter scrap when you're done chain-piecing. Repeat the process each time you begin and end a line of stitching.