Barb, I usually clip the seams together, matching them, before stitching them together with the mattress stitch. You will have to have someone else explain that to you, or google it, as I can't think of a good way to explain it to you. You do it with the right side facing you, and if done properly, it is invisible.

Tami

If you want an almost invisible seam, this is how I always sew sweaters together. Pin both sides together matching knit rows. Starting at the bottom with your tail of yarn. Sew through the knots made by knitting the last stitch. You'll notice that one side of these knots has give and one side is stable and has no give. Go through the side that has no give. Do it on every set of knots and use an overhand whip stitch. You'll notice that the seam blends right in with the knitting and leaves no discernable seam. You can fudge the seam a little if you need to and it will still look good.

Thanks, ladies for your help. I did not finish off any of the parts of this, except the sleeves, because I thought I might want to add a collar. I did find out how to do the mattress stitch. I had never heard of that. I understand that I need to block all of the parts first. What do you do to cover the knitting without putting the iron right on the sweater? Barb

Lay a towel over it. You can just hold the iron over it without touching the sweater, also.

Tami

I spray it with warm water in a spray bottle so it's just damp, and lay it out on a towel. Then block and hand smooth it into the right measurements and leave it to dry on the towel