How To Disengage The Upper (Green) Looper - Singer Quantumlock 14T957DC Detailed Threading Manual

HOW TO DISENGAGE UPPER (GREEN) LOOPER
Turn handwheel towards you until the white rectangular knob is as far to the
right as possible.
To lower the looper push the knob all the way to the left and then push it up.
(To re-engage the looper push the knob all the way to the left and push it down.
Turn the handwheel towards you to raise the looper.)