When knitting socks, pointed needles are used to split stitches in the round. Use pointed needles with tips from a knitting teacher in this free video on yarn crafts.
Now I'm going to show you how to cast on for your sock using double pointed needles. You'll start out with your slip knot like you would for any cast on, and we use the long tail cast on because that gives the most elastic edge. And you're going to be splitting your cast on on to three different needles. So for this sock I need about thirty stitches, and I'm going to split them up. So, let's see, I have two, four, six, seven, so I'm going to put eight on this needle. It's a bamboo needle, so those stitches aren't going anywhere when I let go. I'm going to take my next needle, and I'm going to continue my cast on on to the next needle. And put eight stitches on this needle. And then I'm going to take my third needle, nothing's falling off...it's like a magic trick...and I'm going to put my remaining stitches on to this needle. Once you've got them all on the needle, you're going to have to arrange them to make sure that they're going to lie flat for joining in the round, so they don't get twisted. So it's a good practice to kind of lay them out and make sure all the stitches are facing the same way. Then you pick up your needles, and take your fourth needle, slide your stitches to the end. Put it in like a normal knit, and you're going to take the yarn from where you've last cast on your stitch, and you're going to bring that yarn through the first stitch on the other needle. And then you'll continue working...this is where it gets a little clumsy, but you do get used to it...and you'll begin knitting on to the other needles. And the other ones kind of just hang there until you need them.