Stitching in the Ditch

In order to secure a under-laying piece in place and keep it from shifting or unfolding, sometimes a pattern will instruct you to "stitch in the ditch." What this means is that you will perform a straight-line topstitch, regular-length stitch right down an existing seam line. This helps to hide the stitch on the finished garment.

Before you start stitching, I would line up the needle using the manual knob on your sewing machine so that it will go right into the "ditch" created by the existing seam.

Video below the fold...

Practice It...
In order to practice stitching in the ditch, take a practice simple seam, iron open the allowances, and then, with the wrong side on the inside, fold the seam onto itself (as shown in the video).