The Lever and Knob Assembly (or Front Wheel Height Adjuster) is used to adjust the front height of the mower, and attaches on the front wheels. It can be installed using a socket set and wrench set, and is rated as "easy" to install by our customers. If broken or damaged (likely due to general wear over time) you will no longer be able to move it to make adjustments, and the part should be replaced. This black, plastic part is sold individually. Refer to your make, model and diagrams to ensure this part fits your machine.