Question: How do you fold a NordicTrack C2150 treadmill?

Answer: This is an older model and the folding process is different than on the new models.

Set incline to 0%, remove the key and unplug the treadmill.

Then hold the metal frame and raise the treadmill about halfway.

With one hand hold the treadmill and with the other one pull the latch knob to the left and hold it. Then continue to raise the treadmill until the pin is between the frame and the foot rail. Finally, release the latch knob.

This process may be hard for one person. In order to prevent injuries, take a second person to help you.
And make sure the frame is held securely!