Rational structure is of box construction, adequately designed and reinforced by stiffening ribs, to take care of all types of loadings. This is connected by cross beams. The unbraced legs are hinged near the leg beam attachment. The complete structure is mounted on four wheel base, each having two double rimmed steel wheels provided with flexible bushing to take care of any misalignment. The top beam is firmly fixed on heavily fabricated steel bracket. The crab carriage is in steel section. It is comprised of special crane duty motor, connected to heavy duty speed reducers and are coupled up to a grooved steel drum.Electromagnetic brakes / hydro-thruster brakes are used to control the smooth lifting of weight. The block is equipped with a forged steel forked revolving hook.