Objective: Sew a straight, locked seam at a measured seam allowance and pivot cleanly at a corner on the Janome MC6650.
Every sellable item depends on three core skills: a straight seam, locked ends, and a clean corner. On the MC6650, a straight seam is controlled by the throat plate guide lines etched to the right of the needle. Each line marks a distance from the needle in inches or centimeters — a 1/4" line for quilting/narrow seams and a 5/8" line for garments. You keep the fabric edge riding along the chosen line, not watching the needle, and the seam stays parallel to the edge. Lock the seam so stitches don't unravel: press the reverse (backstitch) button so the machine stitches backward over the first few stitches, release to go forward, and repeat at the end. The MC6650 also has a needle up/down button — set it to needle-down so that when you stop, the needle stays buried in the fabric. That lets you lift the presser foot, rotate the fabric around the needle (a pivot), lower the foot, and continue without the seam jumping. Use a moderate speed; the MC6650's speed slider lets you cap your top speed while learning. Keep both hands guiding lightly — never pull the fabric, let the feed dogs move it.
Example: Take two scrap rectangles, place right sides together, and line the right-hand raw edge against the 5/8" guide line. Lower the foot. Hold the reverse button and stitch backward about 5 stitches, release, then sew forward keeping the edge on the 5/8" line. About 1" before the corner, press the needle-down button, stop exactly at the corner. Lift the presser foot, pivot the fabric 90 degrees, lower the foot, and sew the next side at 5/8". At the finish, backstitch 5 stitches to lock. You now have an L-shaped seam with secured ends and even allowance.
Try it: Cut two 6"x6" fabric squares. With right sides together, sew around three sides at a 5/8" seam allowance: backstitch at the start, pivot at each of the two corners using needle-down, and backstitch at the end. Measure the seam allowance at several points with a ruler — aim for 5/8" within 1/16" everywhere, and check corners are square.