The BO300 is an overdrive guitar pedal that is great for hard driving blues music and the classic hard rock sound. It has three basic controls:

1. LEVEL knob: Use the LEVEL knob to set the overall volume of the pedal.

2. TONE knob: Use the TONE knob to control how "dark" or "bright" you would like your overall tone to sound.

3. GAIN knob: Use the GAIN knob to control how much overdrive you would like present in your tone. 

Use these controls to give your guitar tone that perfect over-driven touch needed for most modern blues and hard rock music.