How to crochet shell stitch: full and half shells

Start with two full shells

1. Chain 14. Single crochet in the second chain from the hook.
2. Skip 2 chains. Make 5 double crochets in the next chain. Skip 2 chains and single crochet in the next chain.
3. Repeat that sequence once. You have 2 full shells and 3 single-crochet anchors.

Alternate the shell rows

1. Row 2: chain 3 and turn; this chain counts as a double crochet. Make 2 double crochets in the first single crochet to form a half shell.
2. Single crochet in the middle double crochet of the first shell. Make 5 double crochets in the middle single-crochet anchor. Single crochet in the middle double crochet of the second shell. Make 3 double crochets in the final anchor.
3. Row 3: chain 1 and turn; it does not count. Single crochet in the first double crochet. Make 5 double crochets in the next single crochet. Single crochet in the middle stitch of the full shell. Make 5 double crochets in the next single crochet. Single crochet in the top of the final turning chain.
4. Repeat Rows 2 and 3. Row 2 has 1 full shell, 2 half shells and 2 anchors. Row 3 returns to 2 full shells and 3 anchors.

Find the middle and keep the edges

A full shell has 5 tops, so its middle stitch is the third. Count from the shell’s beginning rather than estimating the center.

The half shells keep the side edges from turning into large scallops. If your count changes, locate the final turning-chain top and check that you have not added a sixth double crochet to a shell.