Used for mounting an amplifier chassis. Used on '57 Twin®, Blues Deluxe™/DeVille™, Pro Junior™, Hot Rod Deluxe™/DeVille™, Blues Junior®, '59 Bassman®, '63 Fender® Tube Reverb, Bronco™, Bass Breaker™, '57 Deluxe™, Bassman® TV Series, EC Twinolux™/Tremolux™, '57 Champ®, EC Vibro-Champ™, and '57 Bandmaster™ amplifiers manufactured from 1994-Present.