Kenmore 158.1813 Instruction Manual page 13

The stitch length control regulates the length of the stitch you select . THE
HIGHER THE NUMBER - THE SHORTER THE STITCH . Turn only the outer
rim of this control to set the stitch length .
The number on stitch length control indicates stitch number per inch .
The stitch setting you use will be determined by the thickness of the fabric
you are sewing .
A longer stitch setting should be used for thicker fabric or more layers of
fabric .
The middle range of the control is the 10-12 stitch per inch range which is
the most commonly used .
A basting stitch is made by using the longest possible stitch setting - 6 stitches
per inch .
The red marking
- on the control is the setting used for the shortest
stitches such as in Satin Stitching .
This control regulates the width of the stitch you select . THE HIGHER THE
NUMBER -THE WIDER THE STITCH . You may vary your zigzag stitch width
by adjusting this control to the setting you desire .
This control must be on Red "S" in order to do straight stitching .
Turn only the outer rim of this control to set the stitch width .
The center of the control dials the special stitches the machine is capable
of sewing .