Long tail cast on: what, why, and how
The long tail cast on is a commonly used method of casting on stitches: It's simple to work and extremely versatile, suited to various types of knitting that will begin after the cast on, from plain stockinette or garter stitch, to different types of ribbing, lace patterns, or textured knits that feature a mix of knit and purl stitches.
Long tail is named for the long tail that is used as a "second" strand in conjunction with the working yarn (the strand coming from the ball of yarn) for casting on using two strands of yarn.
A good rule of thumb for figuring out the length of the yarn tail needed is three times the length of the row width (or, if working circularly, the round circumference). For example, if your piece measures 6 inches wide, your tail should measure at least 18 inches. Adding a couple of extra inches for safety is never a bad idea.
The point to which you measure the end of the long tail will be where your slipknot is made.
How to work the long tail cast on
Begin the long tail cast on by making a slipknot.
Take a look at the strands hanging from the slipknot snugged on your needle. The working yarn is the end that comes from your ball. Position the strands so the working yarn is on the right and the tail is on the left. Hold the needle and the working yarn in your right hand, the tail in your left, a few inches away from the needle, with a little tension on it and thumb on top of yarn.
a. Create a loop by rotating your thumb under the tail end from behind, then up so your thumb is parallel with the needle and the yarn is looped around it.
b. Insert the tip of the needle upward into the loop formed around your thumb.
c. Secure this position by switching the needle to your left hand while it’s still in the loop on your thumb and, with your right hand, wrap the working yarn counter-clockwise around the needle and sandwich it between the thumb and the needle in your left hand.
d. Now, grasp the needle again with your right hand and with your thumb lift the loop of yarn that’s been sitting on it, bring it up and back and over the tip of the needle.
e. Pull gently on the tail end to firm up your stitch. Remember: not too tight and not too loose.