This tool is designed to adjust worn or improperly adjusted hinges that cause the door to sag. All you do to fix it is slip the tool over the door hinge, hold it in place with one hand, while you open the door with the other hand. This action causes the door hinge to bind while the tool is in place. Open the door only an inch or two past the point where it binds against the tool then remove the tool from the hinge.
