Necchi HD22 Instruction Book page 26

Set the zigzag width dial at "
Sew up the right side of the buttonhole. Stop
the machine when you are directly opposite
the first stitch on the left hand side and raise
the needle.
24
". Set the zigzag width dial at "
Sew a few bartacks and raise the needle from
the fabric.
". Remove the fabric from the machine and cut
the sewing threads.
Insert a pin inside the bartack.
Then cut the opening with a seam ripper.
Take care not to cut the stitches.