Adjusting the height on a Sears Craftsman mower is a fairly simple proposition. Each wheel has an adjusting lever (called a wheel adjuster or a cutting height adjustment lever) that raises or lowers the wheel, which in turn changes the height at which the grass is cut. The key to even mowing of your grass to the desired length is making sure that all four wheels are set at the same height.
Locate the adjuster on one wheel. It's between the wheel and the body of the lawnmower, and it has notches into which a raised lever is positioned.
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Move the lever from the notch it's in by pulling the lever toward the wheel. Slide the lever forward for a higher cut, or backward for a lower cut. Secure the lever at the desired cutting height by pushing it into the appropriate notch.
Repeat this process for the other three wheels.
Double-check that all four wheels have been set at the same height after you've finished adjusting them.
Make sure that the lawnmower is off before adjusting the wheels.