Sew with the stitches falling right in the seam. The seam is the “ditch.”
I used purple thread for my example, but even with purple you can hardly see the stitching. If you look closely, the seam line looks darker than normal. When you stitch in the ditch, match the thread color with the fabric so that it can blend in.
Stitching in the ditch is commonly used on attached bands like a waistband. To do this, push the seam allowance towards the band.
Fold it down with the fold coming just past the seamline. See the pink stitching in the picture, this needs to be covered by the band.
Pin. No more pink stitching showing.
Stitch in the ditch. When stitching in the ditch with a band, one side of the seam is thicker than the other. It makes it a little more difficult to follow the seamline, but it is possible. Just keep the center of the foot lined with the seamline.
This is what is looks like when it’s done. You can see the purple stitching but not a lot. If that thread were white, it would be almost invisible.
This is the back. The band is now sewn down with no raw edges. My fold came down a little too far, but that’s because I pinned it down pretty far. I wanted to make sure you could see what I was talking about.
Here is an example of a skirt waistband. I’m able to show you the stitching in the ditch because it was badly done. The arrows point out where I went up on the band. Even though I stitched this bad, I still wear the skirt and nobody can see my mess-ups.
Good luck with your stitching in the ditch!