I'm pretty sure you're thinking of the custom of hanging stockings over the fireplace. To be accurate, they're not really socks or stockings but something resembling both that nowadays are more designed to hold presents. They're usually red with a white trim at the top. The idea is that you hang the stockings above the fireplace, when Santa Clause comes in the middle of the night he puts presents in them, often maybe candy or something else that's small. In the US, at least, Santa Claus is supposed to keep a list of all the kids who have been naughty (bad, misbehaving) or nice (well-behaved) over the preceding year. Those that were bad get a lump of coal in the stocking instead of presents. I have no idea where this custom comes from or how long it has been in existence, or if it is practiced in any other countries. If you were to visit a US store in the weeks before Christmas, I'm sure you could find stockings made for this purpose.