There are several times when you are sewing that you will need to turn a corner inside out and make it a perfect 90°. Dress makers need to do this for collars and maybe pockets.
When I made some Casserole/Pie carriers I used the technique that I have seen frequently on Sewing with Nancy .
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*A Tutorial Tuesday*
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Insert only your thumb inside.
Hold thumb in corner opposing your finger.
Fold one seam allowance at stitch line over and
hold between thumb and finger.
Fold other seam alloweance over at stitch line
and hold both seam allowances between thumb and finger.
While holding seam allowances between thumb and fingers,
pull out.
You still might have to take a pin
to pull a little tuck out some more.
Usually they turn out perfect,
despite the fact the corners were not trimmed.
If you do trim corners, it's harder to hold the seam allowance.
Usually the untrimmed corner isn't too bulky,
and stitches just fine.
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