Understitch definitions

Understitch

When the seam allowances are stitched to the facing along an edge.
Found on https://www.contrado.co.uk/blog/a-z-guide-sewing-terminology/

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Understitch

when a line of stitching is made on a facing close to the seam through the facing and all the seam allowances. This encourages the facing to sit smoothly and not roll to the outside.
Found on https://www.thesewingdirectory.co.uk/sewing-glossary/

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