SINGER 14T968DC - Manual (Page 19)

Turn Auto Tension Dial to “D”.
Turn Stitch Length Dial to “2”.
Engage Upper Knife. The knife will not trim the fabric when it is disengaged.
1. Open Looper Cover.
2. Pull the movable knife holder (silver screw) to the right as far as it will go.
3. Turn the holder toward clockwise until the knife clicks into a lock position.
Upper Knife Engaged Upper Knife Disengaged
Two-Thread Wrapped Edge Overlock (narrow) page 3