The zigzag stitch is very handy to help in reinforcing buttonholes,
and in temporarily joining two work pieces edge-to-edge.
It is used for stay-stitching around curves for strength and movement,
in stitching stretchable fabrics,
and especially for extra stretchy sewing in knits and elastic.
It is also used to help prevent fraying on looser weave fabrics,
sewing all along the edge of the fabric.
(like Linen, Lugana, Aida and other such wonderful stitching fabrics)
A zigzag allow the seams to have more flexibility
and it is more forgiving on fabrics,
less pulling and puckering.
It does not work as well for piecing quilts together
because the seams don't lie flat enough,
but for a design in quilting the layers together,
it can be interesting.
This stitch was a monumental step
within the sewing machine industry
and from the first attachment produced
to the those of today's standards,
one would be simply blown away
with the progress
and amazing array of different shaped stitches.
Being one to not go down the straightened path
the zigzag is a path well travelled here.
Cheers to back-and-forth stitches used where a straight stitch will not suffice.