A tiny custom painted distortion that cranks everything to 10.
The Box of Rock (TM) is Z.Vex Effect's first "distortion" pedal, highly specialized to simulate the "everything on 10" sound of a classic Marshall ® JTM45 non-master-volume amplifier. You may use the Box of Rock effectively with many different amplifiers, but to get the sound ZVEX heard when they designed it, try it through a Marshall at least once. You may use your guitar's volume control to adjust for the exact amount of distortion you need, all the way down to very clean and clear with most drive settings. You will notice the words "distortron engine" on the Vexter version of this pedal (no, that's not a misprint) on the pedal. This is what Zvex named their distortion circuit... call 'em crazy. On the hand-painted version, the stomp switch on the right is labeled "ROCK" instead, because their paint brushes are too wide for so many small letters.
The Box of Rock also contains an extremely high-headroom, unity-to-50X gain booster with nominal input impedance and low hiss. It is very similar to the SHO boost circuit, with refinements to make it sound more like a standard amp input and less glassy. The boost channel can be used alone or in conjunction with the "distortron engine" channel. The boost channel follows the distortion channel so that the distortion is able to hit your amp harder (at a higher volume) when both switches are engaged, for boosting solos and what-not.
Drive: Sets the amount of distortion. Start around 1:00 o'clock.
Tone: Adjust for treble content. Start around 2:00 o'clock.
Vol: Adjust for distortron engine volume level. Start around 9:00 o'clock.
Boost: Sets the boost level, which is engaged with the left stomp switch. Start around 11:00 o'clock.