I like educating people about how many pairs of socks they should own. Sometimes we have one pair we love so much that we wear them out in a very short amount of time. The fact is you should have at least 10 pairs of socks, for every season, regardless of your preferred fiber. Natural fiber socks are best but there are a lot of people who are allergic to them and need to wear synthetic fibers such as acrylic.
Some people don’t know the difference between wool and acrylic or cotton and acrylic. Some believe the socks they’re wearing are acrylic when they’re actually WOOL. Some think they’re allergic to wool and have never worn wool in their lives. Some are allergic to cotton and linen but can wear every synthetic fiber made. Regardless of fiber allergies or preferences, handknit socks are best.
Whichever type of socks you prefer, the ones you wear the most will eventually wear out! The most common place for handknit socks to wear out is the heel, followed by the ball of the foot. The most common place for mass manufactured socks to wear out is at the toe, followed by the heel. Either way, if you’re trying to save money or just love that pair of socks so much that you can’t bear to part with them, you can always repair them and should repair them.
The two main methods of repairing holey, worn out socks are: Darning, duplicate stitching, and reknitting. I will partially cover darning and reknitting. Darning involves stitching an anchor box around the hole and then weaving from the anchor stitches, over and under, and back and forth, until the hole is filled in and sturdy. I prefer to herringbone weave 2 over and 2 under; and then cross back over to make it all sturdy.
A reknitted heel involves picking up the stitches at the top of the hole and the bottom of the hole, and knitting a heel patch (toe patch, or patch for the ball of the foot) while picking up the old stitches at the sides of the hole, and then using the Kitchener Stitch to graft it all together so it looks nice and neat.
Sometimes, you need to pick up stitches in the middle so you can graft (kitchener stitch) them to the reknit portion during the repair. See the photo below.

Other times, you get very lucky to be able to just grab a few inches of yarn and just sew or weave the hole closed. This works best on holes smaller than a half inch.
There are many different ways to repair your favorite socks. It’s your choice. Do some research. I’ve shared the ones I’m currently working on because I was asked to do so.
*** NOTE: I rarely ever have any of the yarn left over from anything I’ve knit because I tend to use the leftovers in other things after about two years. ***