Abstract: Structural Design of Universal Cavity Pit Wrench, comprising: a sleeving, a mounting panel, a plurality of pillar posts, retainer rods and a plurality of correspondingly functioning retraction springs, for assembling, the plurality of retainer rods are applied to penetrate the mounting panel, get coupled to the retraction spring, then engaged with pillar posts so that the pillar posts are invested with the capability for free retractions, to follow that, the mounting panel is planted into the inner wall of the hollow-set sleeving so that the plurality of pillar posts are neatly deployed on top of the sleeving, so that any nut to be set into the cavity pit, of any type or configuration, may be brought into the cavity pit by the action of those neatly deployed pillar posts, and once all the pillar posts are planted in full into the nut bearing cavity pit loosening or tightening up of an object nut may be proceeded with ease and convenience.