Reinforcing Heels

Heels heels heels.

It is a long-standing truth among knitters that, while socks are spiffingly fun to make, darning socks is hateful. Elizabeth Zimmerman, the mother of knitting empowerment, herself said something like, “I have found many women employ the same darning technique I do. They hold the sock aloft, exclaim ‘darn!’ and drop it in the wastebasket.”

Since yarn companies started blending nylon into their sock yarns, socks have become much sturdier, but no sock lasts forever. So in order to put off having to darn sock for as long as possible, knitters have come up with several ways to reinforce the heels and toes of socks, where holes most quickly develop due to friction with the back of shoes. There are three main ways to accomplish this, and I will describe them below.

Reinforcing Thread

Perhaps the easiest way to reinforce the heel is to simply hold another thread with the working yarn while knitting the heel. You can just double the working yarn, but the fabric this creates is quite thick. Instead, you can purchase a special thread created just for this purpose called reinforcing thread:

Reinforcing thread is not as thin as sewing thread, but is much thinner than the fingering weight used as the main working yarn in socks. It is generally made of 100% nylon or other strong synthetic, so when held together with the working yarn, it helps protect it from wear, and even if the working yarn becomes completely threadbare, a full-blown hole will be much slower to develop. Reinforcing thread is available at your local yarn shop in a variety of colors to coordinate with your sock yarn of choice, and usually comes on little spools or bobbins with enough for one pair. (Your mileage may vary; I’ve never used this stuff, though I’ve sold a ton of it to folks who swear by it.)

  • Advantages: It’s easy as pie, can be used with absolutely any sort of heel, and can also be used to reinforce the toe, which is the second most likely place to develop a hole.
  • Disadvantages: It’s another thing you have to buy, which if you’re as cheap as me, is enough to put you right off it.

Hand-sewn Reinforcement

If you don’t feel like getting another spool of stuff, or if you are using florescent green yarn that you can’t find a reinforcing thread to match, or if you get to the end of a sock and realize you’ve just forgotten the whole issue, this is an easy reinforcement that is done after socks are completed. All you need is the leftovers of your working yarn and a darning/tapestry needle.

This is rather hard to explain, so I’ll show you first.

Turn the sock inside out, thread a 10- to 12- foot length of yarn onto the needle, and start sewing up and down the heel flap, under every other purl bump, alternating purl bumps on the way back. Continue in this fashion until you’ve gone across the whole heel. Make sense? This essentially fills in the fabric of otherwise plain stockinette, making it tighter and a little thicker and thus harder-wearing.

  • Advantages: You can use materials you already have, it works on a plain stockinette heel, and with a bit of fiddling, you can use it on many types of heels (though it’s easiest on a flap heel).
  • Disadvantages: It’s fiddly, and it’s more finishing work. If you already dislike finishing, then you may find yourself majorly procrastinating on this one. (Note last months socks in the picture above. I still haven’t finished reinforcing them, and I don’t even mind finishing that much.)

Slip-stitch Reinforcement

This method is very popular today; I see it in most contemporary sock patterns with a heel flap. If your sock pattern uses this method, it will have specific instructions on how to carry it out, but the basic idea is this: on the heel flap, slip every other stitch of the right side row. (Slipping a stitch just means literally sliding the stitch purlwise from one needle to the other without knitting or purling into it.) Deceptively simple, but this little action actually makes a thicker fabric. Here’s how.

Those big fat V-s standing out are the stitches being slipped every other row. You can see the smaller in-between stitches behind them. The slipped stitches are essentially stretched over the height of two rows, which compacts the fabric vertically.

At the same time, since you aren’t working the slipped stitch, the working yarn goes around the back of the slipped stitch and is tightened when it works the next non-slipped stitch. This further compacts the fabric horizontally. Isn’t that cool?

  • Advantages: You don’t have to buy or find any extra equipment to do it, and you can work it right into the sock. Also, I think it’s fun to do, makes a neat-looking fabric, and makes me feel clever.
  • Disadvantages: This can really only be done on a flap heel (sorry short-row-heel lovers) and isn’t really useful for toes. And as cool as the fabric looks, it just doesn’t fit in with the design aesthetic on some socks. But sometimes I say screw it and use it anyway.

You don’t need to reinforce a heel if:

  • Your heel is knit in fair isle (this already makes a doubled fabric, and for heaven’s sake you’ve done enough fiddling),
  • You are knitting socks that won’t be worn in shoes (like sleeping socks, house socks, or socks for someone in a wheelchair),
  • You only wear clogs, or
  • For some reason you really like darning. (If you do, don’t tell anyone, or you will find daily shipments of holey hand-knit socks sent you by express post from us lazy sock knitters.)

4 thoughts on “Reinforcing Heels

  1. My question has to do with heel flaps

    Some patterns say Row 1: sl 1, *k1, sl1* rep from * ending with k1
    Row 2: sl 1 purl across
    Repeat rows 1-2 until heel flap measures 2 1/2″ ending with a purl

    On another pattern row 2 says sl 1 as if to purl, purl to last stitch in row, k1.
    Repeat rows 1-2 to desired length. end with a completed purl row.

    I am planning to continue the k2 p2 ribbing down the instep. My son has rather skinny feet.

    On the website under stupid knitting tricks it says This is a simple trick that produe a neat and attractive finish on a selvedge edge. All you have to do is slip the first stitch of every row purl-wise and knit the last stitch of every row. I think this is basically the same as procedure 2.(But wonder how it would be for socks– if it would create larger holes to deal with or add extra irritation for wearers foot etc…)

    What is the best way to do the heel flap that would create the least amount of friction on the foot inside the sock. I am working on socks for my son who is in the military and do not want to create any friction for his foot or irritation for him because his Mom knitted him some socks.
    I have 9 inches of ribbing done on two socks and am ready to work on the heel flaps.
    I hope I don’t freak out with every step!!!

    I appreciate any help and advice you can give me. I am sure my son appreciates it even more.


  2. Interesting question. If I understand right, the only real difference between the first option you mention and the second is that the 1st says to purl the last stitch of row 2; the 2nd says to knit the last stitch of row 2. This might ever-so-slightly alter the appearance of the slipped stitches along the edge of the heel flap.

    I doubt it makes any significant difference, though I confess I have not tried the second method! Play around with it and see which looks right to you. Personally, I suspect that the real thing that makes a difference in comfort is that, when picking up for the gusset, you only pick up the one side of the “V” that is closer to the right side of the flap. But no matter how you do it, even if you twist as you pick up, you are making pretty big loopy stitches along the edge of the heel flap that are very unlikely to be irritating. Have you had trouble making that part of socks comfortable?


  3. How about knitting a double thickness with double the stitches? Or, knit another heel or toe and sew into place on the inside. When signs of wear indicate, remove and sew a new heel to the inside again.


    1. Thanks for your ideas… I certainly did not exhaust all the possibilities! I had probably knit a dozen socks by the time I wrote this, but have since knit two dozen more pairs at least. Now many of this early batch are wearing out, mostly on the bottom, so I have to figure out something totally different to fix them.


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