SINGER 1748 - Manual (Page 47)

GB
Turn the stitch selection dial so that the pointer is set to the
straight stitch position.
Generally speaking, the thicker the fabric, thread and needle,
the longer the stitch should be. For a fine stitch set length at "1"
or "2".
For gathering set to straight stitch, with stitch length at "4". Do
2 rows of stitching ¼ of an inch apart. Remove from machine,
hold bobbin thread and gather fabric to desired fullness.
Choose your needle position, from left position to right needle
position by changing the stitch width dial from "0" to "5".
40
Straight stitching and needle position