Today we're talking about coral stitch. Also called beaded stitch, German knot stitch, or snail trail, this stitch can be used singly to outline shapes, or worked in rows spaced closely together as a filling stitch, in which case you'll want to position the knots between those in the previous row. Here's how you do it:
Bring your thread to the front on the righthand side of your line and lay it along the line for a short distance, holding it in place with your thumb.
Keep holding the thread and take a small stitch from just above the thread to just below it. Your thread will form a loop and your needle should stay inside that loop.
Keeping your thread taut, begin to pull it through until a knot forms.
Lay your thread along the line again and take another small stitch in the same way. You can space your knots at whatever distance you like, just keep them evenly spaced as you continue along the line. When you come to the end take your thread to the back and end off (weave threads into back). That's it.
Here's a side view so you can see the knots better.
For a filling stitch, complete another row parallel to the first, spacing your knots so they fall in the open spaces between the knots on the first row. Then continue to alternate the knots as you fill your shape. Use a second color if you want a striped effect.