How to do the long-tail cast-on

The long-tail cast-on gives you a stretchy, tidy edge, and it's the one worth learning first. It takes about ten minutes to get wrong twice and right on the third try. You need yarn and one needle.

It's called long-tail because you work with two strands at once: the tail hanging off your ball and the working yarn still attached to it. The tail builds the bottom edge. The working yarn builds the first row of stitches. That's why one pass gives you a cast-on and a knitted row in the same motion.

How much tail to leave

Run out of tail at stitch 58 of 60 and you start over. Two ways to avoid that:

• Wrap method. Wrap yarn around the needle once per stitch you need, then add about six inches. Slide the wraps off and that length is your tail.
• Inch-per-stitch rule of thumb. For worsted weight on a US 8 (5.0mm), roughly half an inch of tail per stitch, plus six inches to weave in. Thicker yarn needs more, laceweight needs less.

When in doubt, leave too much. Extra tail costs you a snip. Too little costs you the whole cast-on.

The steps

1. 1Measure your tail and make a slipknot there. Put the slipknot on the needle and hold the needle in your right hand. That slipknot counts as your first stitch.
2. 2Let both strands hang down. Slide your left thumb and index finger between them, so the tail runs over your thumb and the working yarn runs over your index finger.
3. 3Close your remaining three fingers over both strands to hold the tension. Your left hand now makes a shape like a slingshot, with a V of yarn between thumb and finger.
4. 4Bring the needle tip up under the loop on the front of your thumb.
5. 5Carry the needle over and grab the strand on the front of your index finger, from right to left.
6. 6Pull that strand back down through the thumb loop.
7. 7Slip your thumb out and re-hook it under the tail strand, tugging gently downward to snug the new stitch against the needle. Not tight. Snug.
8. 8Repeat steps 4 through 7 until you have the stitch count your pattern asks for, counting the slipknot as one.

If it goes wrong

The edge is so tight the first row is a fight.

You're pulling the thumb strand down hard after each stitch. Snug it until the stitch touches the needle, then stop. If your hands won't cooperate, cast on over two needles held together and slide one out at the end.

The edge is loose and floppy, with gaps between stitches.

The opposite problem, and less common. Tug a little more after each stitch, and check you aren't casting on over two needles out of habit.

You ran out of tail partway through.

There's no rescue. Pull it all out, measure with the wrap method, and start again. This happens to everyone roughly once.

The stitches are twisted when you knit row one.

Each stitch should sit with its right leg in front of the needle. If yours are backwards, you've likely hooked the index-finger strand left to right instead of right to left in step 5.

When to use something else

Long-tail is the default for flat pieces, ribbing, and most sweaters. Two cases where it isn't the right pick:

• You need a very stretchy edge, like the cuff of a top-down sock. Use the German twisted cast-on, which is the same motion with one extra hook.
• You'll knit from the cast-on edge later, like a provisional start for a scarf you'll extend from both ends. Use a crochet provisional cast-on so you can unzip it.

For a first scarf or dishcloth, neither applies. Long-tail and go.