If you are looking at the baler from the front, open the door that flips up just in front of the belts. On the left side under the door, there is a control valve. There is a round knob that you need to turn clockwise to tighten the bales. Actually there is a doule knob. The one behind the outer knob is a locking knob. Turn the rear knob to unlock the outer knob and then turn the knob in a turn or two. The gauge munted on the front of the baler should register a higher reading. Just don't tighten it so much that the gauge goes in the red while feeding hay into the baler.