A modular connector is disclosed that comprises of a middle-plate, a plurality of sectioned-base-plates, and a plurality of locking-plates. The middle-plate and the plurality of sectioned-base-plates have a plurality of slotted holes to enable faster construction and deal with construction tolerances efficiently. Also, a plurality of grooved surfaces on the sectioned-base-plate and the locking-plate provide a system so that bolted-connected modules do not slide and remain at initially its aligned position. Disclosed is also a method for assembling a modular building.