There are multiple ways to attach crocheted pieces together. You may need to attach pieces of a sweater, for example, or attach blocks together to make a throw. The three common ways to attach crochet pieces are sewn seams, crocheted seams, and Join-As-You-Go techniques. You can go to the Ultimate Guide to Join-As-You-Go Crochet to learn more about those techniques. Assembling a project has two components: placing the pieces together so they are correctly lined up and attaching them. Patterns may give instructions on the suggested way to attach pieces together, but often will not give detailed notes on lining them up.If you are attaching pieces that are the same size and stitch count, you can line up the stitchesso they are in pairs, and then attach each stitch to its paired stitch. If you are attaching pieces that areslightly different, such as a flat piece and a curved piece, or the end of a piece to the side of another piece, you may want to pin the pieces together before you start so they line up neatly. Pinning pieces is also recommended for larger pieces. Pinninghelps keep on side from being stretched out or the seam from being uneven. Regular sewing pins often will not work with crocheted pieces, since the yarn is too thick, and the existing spaces are too big. Instead, use Knit Klips or Stitch pins (locking stitch markers). A pattern may call for a particular method of attaching pieces together, or it may just say to attach them or to sew them. Use whichever method you are comfortable with and that gives you a seam you are happy with. You may want the seam to be invisible, or you may decide you like it as a design feature and want it to be obvious.Using the same color yarn as the project is made in will help the seam to be invisible. Generally, projects are sewn together using the same yarn they were made with. If a yarn is very bulky or textured, use a finer, smooth yarn in a matching color to attach them. In this video Marly Bird shows you three ways to sew crochet seams with variations of crochet mattress stitch. Another way to seam crochet is to whipstitch pieces together. This technique is especially suited for attaching the ends of twopieces together. Place the pieces edge to edge with the wrong sides facing up and go from one side to the other side repeatedly, always in the same direction. Working in the front loop of one side and the back loop of the other side, as shown in the picture, will help make the seam more invisible. Another common method is to crochet the pieces together, either with a slip stitch seam or with a single crochet.