I've been working on a baby dress and I'm just about done...except the last directions say for the buttonhole row: Work in rib over first 3sts, bind off next 4 sts, work in rib to end. I know how to bind the sts, but what does it mean to work in the rib? The past 8.5in before that it was k2, p2 so there is a rib pattern going on but I don't know what it means to work in the rib. Also for the next row it says: work in rib, casting on 4 sts over bound off sts. continue to work even for 4 rows. Again, I don't know what working in rib means, and I imagine I cold figure out how to cast on 4 sts over the bound off ones...that sounds pretty straightforward, and then do the same thing for the next 4 rows.
Work in rib just means to work the same rib pattern you've been working, knit the knits and purl the purls. You'll work 3 sts keeping in pattern then bind off 4 sts and then pick up the rib pattern again. When you do the next row and come to the bound off stitches you can use a knitted cast on to add the 4 sts back. Just move the right needle to your left hand, cast on 4 sts, move it back to your right hand and pick up the rib pattern where you left off. HTH