Self-propelled lawn mowers work on a drive system (making them vehicle-like) that requires the operator to squeeze a bar (called a "bail") on the handle to engage the mower. After that, the mower moves forward on its own (you don't have to push it) Excellent quality petrol lawnmower for long life and easy work. Light-weight grass box.Central height adjustment with 5 positions. Large knob is easy to grip.