Once the leg is complete, you knit the heel. It may look complicated, but only a few simple steps are involved. To shape the sock so that it fits around the curve of the foot, the gusset heel consists of three steps—knitting a heel flap, shaping the bottom of the heel, and decreasing for the gusset. The example sock contains 64 cast-on stitches.
Knit the heel flap
The heel flap is typically knit on half the total number of sock stitches and in a slipped-stitch pattern for thickness and durability. You knit it back and forth (not in the round) to produce a flap for the back of the heel.
Knit one needle (25%) of the sock’s stitches as follows:
Row 1: * Sl 1 pwise wyib, k1 *, rep from * to * across.
Example sock: Work 16 sts in patt.
Turn the work so that the inside of the sock is facing you.
Work across two needles (50% of the sock’s stitches) as follows, working all the stitches onto one needle:
Row 2: Sl 1 pwise wyif, p across.
Example sock: Work 32 sts in patt.
Repeat rows 1 and 2 until the heel flap is square—work as many rows as there are stitches in the heel flap.
Example sock: The heel flap is 32 sts wide and 32 rows long.
You can figure out how many rows of heel flap you’ve knit by counting the large chain stitches on either edge. You’ll have half as many chain stitches as the number of heel flap stitches when the flap is done!
Turn the heel
Turning the heel involves the use of short rows to shape the “cup” at the bottom of the heel. Short rows are rows where you only work part of the stitches in the row, leaving some stitches to be worked later.
Knit across a prescribed number of stitches—usually a little more than half of the stitches.
Example sock: K 18 sts.
Decrease by ssk, then k1. Turn the work to the wrong side.
Slip 1 purlwise with the yarn in front, purl 5, p2tog, p1.
Socks with different stitch counts may prescribe a different number of purl stitches on this row.
Continue to work short rows as follows:
Row 1 (RS): Slip 1 pwise, knit to 1 st before the gap created in the previous row, ssk, k1, turn.
Row 2 (WS): Slip 1 pwise, purl to 1 st before the gap, p2tog, p1, turn.
Repeat these 2 rows until all the stitches of the heel flap are worked, ending with the RS facing for next row. If not enough stitches remain to complete the p2tog, p1 at the end of the last WS row, work as p2tog.
Example sock: 18 sts remain.
For a deeper heel, work more rows in the heel flap before turning the heel. For each 2 additional rows you add to the heel flap, pick up an additional stitch on either side of the heel flap when preparing for the gusset.
Make the gusset
The gusset consists of two parts: picking up stitches to connect the heel flap with the rest of the sock and working decreases to shape the sides of the foot.
Knit across all heel stitches (example sock: 18), then pick up stitches with another double-pointed needle as follows:
Insert the tip of the right (empty) needle below both legs of the slipped-stitch column along the edge of the heel flap. Wrap the yarn around the needle as if you were knitting, then pull the new stitch through the work to create a new loop on the right needle.
Continue to pick up stitches along the edge of the heel flap, 1 stitch for each slipped stitch along the edge, until 18 stitches are picked up.
Knit across the instep stitches that were held during the knitting of the heel, continuing any pattern if you desire, then pick up 18 more stitches along the other side of the heel flap. Knit across the heel flap stitches—this needle is now called Needle 1 and is the first needle of the round.
To prevent a hole at the top of the heel flap, you can pick up an extra stitch at the junction between the heel flap and the instep. Continue with the decreases as written until the original number of stitches remain.
Work decrease round as follows:
Needle 2: Knit to the last 3 sts, k2tog, k1.
Needle 3: Work across in patt.
Needle 4: K1, ssk, k to end of needle.
Knit 1 round even.
Repeat the last 2 rows until 64 stitches remain, or the original cast-on number.
To prevent holes from forming at the top of the gusset, pick up an additional stitch at the very corner of the gusset where it meets the instep (top of the foot) on either side of the foot. Continue the decreases as given.