Back stitch is another straight stitch variant. Instead of a dotted line, it creates a filled in line. In fact, it can look a lot like double running stitch, but the solid line is created in one pass of the needle!
By varying your stitch length, you can work this line around curves, making great outlines. The spots where your needle comes up and down in the fabric will likely be visible, depending on how fuzzy your thread is. If you want a smoother line, try using stem stitch (described next week from now).
Hint: The tighter a curve is, the shorter the stitches should be.