When should the course adjustment knob be used?

The course adjustment knob should be used when initially focusing on a specimen under low power magnification, typically with a microscope. It allows for quick and significant changes in the stage height to bring the specimen into the general focus. Once the specimen is in focus, the fine adjustment knob should be used for more precise focusing, especially at higher magnifications. Using the course adjustment knob at higher powers can risk damaging the slide or the objective lens.