A mechanical bracket for positively engaging of a generally cylindrical tank such as an SCBA tank in an inverted position mounted to a planar surface such as within the back of a fire truck seat. The apparatus includes a uniquely configured top clamping member which is pivotally mounted to selectively engage the upwardly facing bottom of the tank as well as including a bumper immediately thereadjacent which is adjustably positionable for abutment with the lower end of the tank which is facing upwardly. A uniquely configured foot plate is provided having a tank receiving zone defined therewithin for holding of the upper valving area of such tanks. A unique locking mechanism and release mechanism is also provided.