as with a hooking device 12 which is displaceable between the end of the boom and a stop 13 such hooking device 12 consists of two parallel block and tackle mechanisms from which is suspended a fork 14 by way of cable 70 said cable 70 passes over a first block 64 and goes backwards horizontally to a second block 66 from which it returns forward to embrace a third block 68 being the cable end 72 made fast to the hooking device frame 60 which can be mounted on the crane boom by way of mounting hole 62 and bolt the third block 68 of the block and tackle mechanism are joined by a sliding axle 74 that can slide horizontally on a corresponding frame slot 76 when the sliding awe 74 is pushed forward by crane stop 13 as a result of the entire hooking device 12 being forced upon the stop 13 when the crane boom retracts as can be seen on fig2 4 5 and 6 the fork 14 presents two bumps 25 for retaining the flange 26 and a bearing 78 through which a vertical push rod slides 15 fixed by a cube 84 in an articulate manner to the frame 60 thanks to a bolt 86 that passes through two parallel lugs 82 of the transverse member 80 of the frame 60 over the central part of the top of the container 4 is provided an opening mechanism 16 its housing 24 has a cylindrical shape with perimetral flange 26 so as to permit the coupling of fork 14 of the hooking device 12 integral to the crane boom 3 a push button 21 protrudes from the top of the mechanism housing 24.