Adjustable wrenches are designed to provide a wide range of sizes in a single tool and are a convenient wrench for service and repairmen, linemen, etc. They are not intended to replace fixed opening wrenches for production or general service work. Properly used, this wrench tightens and loosens a wide range of nuts and bolts with light duty needs.
Do not use an adjustable wrench to free a “frozen” nut or to final tighten a nut. Never pull on a loosely adjusted wrench. Never use a hammer or extension on this wrench.
Source: Hand Tools Institute