The thread path that you use to join (sew together) square stitch beadwork depends on whether you're joining rows or columns.
How to Join Square Stitch Rows
The diagram above shows the thread path for stitching together two horizontal rows of square stitch. (The beads are shown spaced apart for better viewing of the thread.) Notice that it is the same path that you use to add beads with square stitch, except that the beads are already in place.
The thread path for joining two vertical columns of square stitch is shown on the next page.