substantially square cross section with a rail 9 at each corner with through holes 10 at a regular mutual distance along the leg the leg 4 can also be called octagonal in cross section having the rails as some of its sides the leg 4 may also be triangular in cross section having for instance three rails be round of elliptical in cross section or may have another cross section the legs shown with four rails however have the advantage of several actuators described below in the embodiment shown the leg can have a connecting bar beam or plate substantially parallel to the normal of the rails 9 in order to provide rigidity and strength against forces working substantially normal to the rails 9 in an embodiment several plates are provided which connect all the rails 9 and in most cases also the plates 20 connecting the rails 9 jacking device 5 has a frame 8 which is coupled to the vessel jacking device 5 further has actuators 11 11 u2032 in this embodiment each comprising two hydraulic cylinders in particular these hydraulic cylinders are double acting cylinders which again allows an increase in operational speed the actuators can also be of an electrically driven type for instance comprising one or more servomotors these types of actuators are not very common in the offshore field however actuators 11 11 u2032 have a first end 12 12 u2032 attached to frame 8 the actuators extend along the leg 4.