Using afghan crochet hook, chain width of afghan.
Insert hook into second chain (ch), yarn over (yo) and draw yarn through stitch (st). * Insert hook into next ch, yo, draw through st *, repeating from * to * across. On last ch, make sure to insert into ch, not single st.
Yo, draw yarn through one loop on hook, * yo, draw yarn through 2 loops on hook * repeating from * to * across. One loop remains on hook which begins next row.
With first loop on hook, insert hook into next front vertical st, yo and draw through st. * Insert hook into next front vertical st, yo and draw through st* repeating from * to * across, again making sure to insert into ch, not single st.
Continue Row 2 and 3, ending with Row 2, for length of afghan.
To finish top row, ch 1, single crochet (sc) across (inserting hook into single vertical and next space, pulling yarn back through both to finish sc - this closes the gap between rows).
Sc around rest of afghan with 3 sc in corners.
This pattern is mostly used for blankets. Usually some kind of cross-stitch is added for unique decoration or personalization.