The last thing to finish the sagums is necklines. It's my favourite work as far as sewing, my great granny taught me this.
First take a piece of fabric, the inner "circle" should be the same as the neck's (when laid face sides together!).
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This isn't very exact, cutting these wasn't my business:-P
Than sew it 3-6mm from the edge, according to the sort of fabric. Face to face!
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Fold the piece to the wrong side and sew as far from the inner edge as you wish.
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I sewed one more line. Cut the piece and zig-zag it.
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Uf, I already have three costumes completed ;-)