Depending on where you live in the world, you can find a wide variety of grass in your yard. In the Untied States, most lawns consist of either Bentgrass or Kentucky Bluegrass, though other types of grass do exist. Depending on the type of grass and the cutting season, you may find yourself adjusting the lawnmower's blade height. The catch is that in adjusting the height of the blade, whether it's a push mower or a riding mower, you never actually touch the blade.
Examine the type of grass that is to be cut. This factor determines the height that the mower should be adjusted. For instance, Rye and Kentucky Bluegrass should be cut at between 1 1/2 inches during the summer, and 2 1/2 inches during the fall.
Locate the lever to adjust the height of the lawnmower. Depending on the age of the mower you may have a single universal lever that controls the unit, or latches on each individual wheel.
Adjust the height of the mower by moving the lever or latch to the proper notch for the height you want. The general rule for lawnmowers is that each notch signals 1/2-inch and certain mowers will have them labeled. As mentioned in Step 2, if your mower has a latch for each wheel, you will have to adjust each wheel to the same notch placement.
Find out the type of grass you're going to be cutting. Different kinds of grass need to be cut at different heights in order to grow in fully. Fescue grass, for example, should be cut at 1 1/2 inches during the summer, while Centipede grass only needs to be cut down to 1 inch high.
Locate the height adjustment knob or lever on your riding mower. For most riding mowers, this is located somewhere on the left side of the seat.
Lower the mower's deck by either turning the knob counterclockwise or by pulling the lever toward the rear of the mower. If using the lever, either pull inward or push away from the seat to lock into place when at the appropriate height.
Wear gloves when working with your lawnmower. You will be met with resistance when dealing with push mower wheel latches, and can cut yourself if your hand slips.
DO NOT attempt to lower your lawnmower's height while it is running.