Basting holds the three layers together to prevent shifting while quilting.
For hand quilting, baste using a long needle threaded with as long a length of sewing thread as can be used without tangling. Insert needle through all layers in center of quilt and baste layers together with a long running stitch. For the first line of basting, stitch up and down the vertical center of the quilt. Next, baste across the horizontal center of the quilt. Working toward the edges and creating a grid, continue basting to completely stabilize the layers.
For machine quilting, pin-baste using nickel-plated safety pins, instead of needle and thread. Begin in the center of the quilt and work outward to the edges, placing safety pins approximately every 4".