The Navajo Plying technique allows you to turn a single thread of yarn into a 3 ply yarn. It is also used to create various color effects with multi-colored fiber. When spinning the singles, keep in mind to spin 3 times the length of the yarn you want when it is finished.
Put the bobbin of single yarn into the lazy kate of the wheel and an empty bobbin into the flyer. Thread the single through the loop of the leader on the empty bobbin. Tie the end of the single to form a loop large enough to slip your hand through. Treadle the wheel in the counter-clockwise direction (or the opposite direction from the way the single was spun), while reaching through the loop and pulling the single through to form a new loop. Proceed to chain with the back hand, while pinching and releasing the yarn with the front hand. This technique is similar to chaining stitches in crochet.