Use this technique to cast on 2 rows of stitches at the same time, so that you can knit outwards in both directions, with a seamless join in the middle. The tutorial is written for using a circular needle.

(Note: The original technique, by Judy Becker, was given on knitty.com - head to that page for a more thorough how-to, which is focused on using it for sock knitting.)

Here's an animation to accompany the photos and written how-to's...

make a slip knot, yarn tail approx 4 times length of cast-on; place on needle (this is first cast-on stitch)

hold (circular) needles parallel, pointing left, slip knot on top - in left hand, hold yarn with tail up over index finger, yarn end which is attached to ball down over thumb

or do not make a slip knot, and instead loop yarn around top needle, so that the tail is going up over the needle and down in front, then back and up over index finger, and the attached yarn down behind the needle and around thumb - work everything as explained below, pulling the first few stitches tight to steady the loose loop

bring bottom needle up over top strand of yarn, then down so yarn loops around front of bottom needle, through middle of needles, to the back (this is first stitch cast on to bottom needle)

bring top needle down over bottom strand of yarn, then back so yarn loops around front of top needle, through middle of needles, to the back (this is second stitch cast on to top - slip knot was first)

repeat those two movements - wrap top strand around bottom needle, then wrap bottom strand around top needle - until you've completed your cast-on stitch count

end with a bottom stitch, so there are the same number on each needle

to begin knitting, turn needles so they are facing right (now last cast-on stitch is on top needle, since they've been flipped)

pull bottom needle out so the bottom cast-on stitches are on the cord, and you can use bottom needle to knit into top needle stitches

yarn tail is coming down from top stitch - let that hang loose, in back, and bring working yarn from bottom up to the front, to knit across stitches on top needle (pulling tail strand to tighten it as you knit the first stitch, or after knitting it)

when working across bottom stitches, around other side, knit (or purl) into back loops to untwist them