It's called an all-in-one facing, and you can use it for sleeveless dresses, shirts, vests, basically anything that doesn't have sleeves and needs to have a finished seam around the neck and arm holes. Also, it'll make anything sleeveless reversible, if that's your goal.
The best part about it: No hand sewing! After following a particularly obnoxious commercial pattern that required me to hand stitch around a sleeveless arm hole, I thought this tutorial was due.
This is our final goal. See how the front of this garment has perfect side and shoulder seams with no top stitching?
Well, the inside looks exactly the same. So nice and neat, and again, reversible! (er, not this dress. but it could be, you know?)
Let's get started, shall we? For the purposes of keeping this tutorial to a mere 2,352 pictures instead of twice that many, I'm going to skip any discussion of closure. Not the emotional kind. The zipper/button/velcro kind. But you can adapt this technique to whatever your pattern or imagination calls for.
Let's assume you've cut out a bodice front and back:
You'll also need a lining or facing front and back:
(this picture shows a lining, which is what you'd use if you want to make something reversible. Otherwise you can just use a facing, which would just cover the area around the neck and arm holes, leaving the majority of the bodice unlined)
Sew your bodice front to your bodice back right sides together at the side seams:
Sew your lining front to your lining back right sides together at the side seams
Turn your bodice right side out. Keep your lining inside out. Slip your lining down over your bodice, lining up all neck and arm curves. Your bodice and lining fabrics should be right sides together.
Now pin your bodice to your lining. Place a pin about 2 inches down from the shoulder seam on each side of each strap (you'll use 8 pins here)
Put another pin at each of the side seams to hold everything together.
Sew the bodice to the lining, stopping when you get to each of the pins near the shoulder seams. You'll be sewing 4 different areas here - the front and back neckline and each underarm area. Depending on what kind of closure you're using, your back bodice may be in two pieces. That's ok, it doesn't change the process.
Clip the seam allowances close to the stitching line.
Turn the whole thing right side out through the bottom opening and press. Now everything is sewn nicely together except the shoulder seams.
Turn your bodice inside out so the two bodice shoulder straps are right sides together.
Pin the shoulder straps right sides together, moving the lining straps out of the way.
Sew the straps together.
Twist the lining straps so they are also right sides together and pin. This may take a little coercion, but it'll work (this is where you'll be glad you left a good 2 inches free).
Sew the lining straps together.
Turn the whole thing right side out. See how both shoulder seams are now finished without exposed seam allowances on the outside:
and the inside?
That's good. The battle is halfway won. Now we just have to do something about these raw edges:
This is the part where some patterns I've seen will tell you to hand stitch the shoulder seam closed on one or both sides. But that can be avoided! Moving on....
If you're making a reversible top, at this point you need to sew the bottom edge closed. But you'll need to leave a hole to turn right side out at the end, and yes, you'll have to hand-sew that opening shut. (Or you could top stitch around the bottom edge and close your opening in the process.) But if this is a bodice for a dress, you can leave the bottom edge open and continue with these instructions.
Turn the whole thing right side out.
This is the part that is difficult to show in pictures and may seem strange, but stay with me. Separate the bodice and lining.
Reach your hand up between the two toward the shoulder.
Pinch the two shoulder seams between your fingers.
and pull the whole thing down and out as you remove your hand.
(If you've sewn the bottom shut for a reversible top and have only left a small opening for turning, it'll be harder to do this step, but just keep working at it. You'll have to pull the whole shoulder strap through your opening.)
Keep pulling until you see your two unfinished seams on either side of the shoulder strap and your shoulder seam is laying flat.
Now you'll be able to see the two seams that you sewed 2 inches shy of the shoulder seam. Put a pin where each of those seams ends.
And now sew between the pins, smoothly connecting the two stitch lines. Make sure to back stitch at the beginning and end.
Pin down the opposite side of the shoulder strap.
And sew a connecting line on that side too. This side will be harder because you'll have a lot of fabric bunched up within the strap that you'll need to keep out of the way of your needle. Just go slowly and stop occasionally with the needle down to shift the fabric and squish it out of the way as necessary.
It'll kinda look like a stuffed dog bone at this point.
Now just pull the shoulder strap back through and right side out. Press the whole thing well, repeat the steps to finish the other shoulder strap, and you're done! If necessary, close the hole at the bottom edge like I mentioned.
Or if you're making a dress, you can now attach the skirt to the bodice.
And that's all I've got on all-in-one facings! Have fun with it, this technique will really make your garments look clean and professional.
note: For dresses that have a back bodice split into 2 pieces (such as dresses that will be finished with a zipper or buttons), this tutorial shows a much easier way to do an all-in-one facing. But if you want to have a keyhole opening that doesn't extend all the way to the waist seam like the dress above, you have to do it this way. sorry :)