You will need
  • Holey socks, Gypsy needle, yarn or a suitable contrasting color, light and a little patience.
Before you begin, you should decide what you want to get in the end: a sock that looks like new, with invisible mending or brand new, something the designer product. Having made this decision, you choose threads of the same (first embodiment) or contrasting color (for option 2) and get to work. You can darn on the front and on the reverse side of the product.
Need conveniently located near a bright light source to see the yarn, folded in half, in the eye of the Gypsy needle (if you can't do it directly, you can pass a regular string into the loop of the thicker threads, and get so thin thread and it is thick). You then take a clean washed and dried the sock insert inside of it a large lamp (or a special wooden beater with a large round tip), dividing the surface of the sock so that the hole was the most sprawled on the top of the bulb.
You can start the work. If the small hole in the toe, or even planned, it's better to start with circular of strengthening the edges, then go to the serial thread back and forth from edge to edge with the aim of creating artificial patches. You will feel when to stop, because the patch should not interfere with you when walking.
If the hole is big, you will have to work hard: after processing a circular hole, in order to hold on to territory against further spread, it is possible, armed with a small thick flap of soft tissue (such as stretchy knitted fabric), sew it into a hole, fixing from end to end, piercing stitches through the entire thickness of the edge of the sock and support tissue. It is very important to be very careful that the joint region is quite dense, but at the same time not injure the skin of the feet when walking.
After basic work is completed, and the hole is completely hidden under a good layer of fresh yarn, you need a way to hide the tip of the thread, this is best done in the fabric of the sock, not latkes.

The long life of your socks!