A shell stitch is a decorative type of crochet motif. A basic shell stitch begins with a single crochet stitch of yarn, complimented by multiple long stitches spreading out away from the base in an arcing pattern. When completed, the resulting motif element takes the shape of a small fan or half shell. Typically, each individual arc is attached to the next to create rows, which are then used as trim for blankets, garments, and other crochet items.
In addition to borders and trim, shell stitch rows also appear as completed fabrics. By attaching rows of shell stitches to each other, the resulting fabric takes on a delicate appearance similar to lace. Shells are staggered, often incorporating color schemes to further highlight the decorative pattern. Such fabric is common in doilies and other items where a fancier or more intricate design is desired. In terms of appearance, the finer the yarn used the more delicate the result.
Methods for creating shell stitches vary. According to crochet standards in the United States, a basic shell stitch requires a single crochet, skip two. Next, complete five double crochets, incorporating the doubles back into the initial single crochet. Skip two again and finish with a single crochet into the center-most double crochet. Variations, depending on cultural practices and artistic design, include such changes as substituting triple crochets in place of doubles.
The use of a standard solid shell stitch to create a border allows the row to attach to any crochet pattern by virtue of half-staggering, a general stitching method that is easily incorporated into virtually all motifs. Half-staggered shells are done by stitching new shells into open single crochets in granny squares and other crochet patterns. The same generalized stitching methodology also allows rows of solid shells to combine easily into each other to create fabric. Once the first row is complete, the next row attaches and begins new shells using the open single crochets between the shells on the first row.
A cousin to the shell stitch, the fan stitch further modifies the concept of arcing patterns. A fan stitch begins much the same as a shell stitch, but with minor changes. Instead of using five double crochets into a single crochet, a fan stitch uses only two double crochets. The double crochets are then connected to chains, where more double crochets finish the design. As a result, a fan stitch provides a more intricate variation to the shell stitch.