such that a supported leg is held in a position corresponding to the position of that leg in the assembled state of the jacket structure the assembly guide further includes a plurality of connecting devices for releasably connecting one of the legs to one of the supporting towers application_number US 201213444917 A description in the diagrams like numbers refer to like objects throughout objects in the diagrams are not necessarily drawn to scale fig1 shows a jacket structure 1 used in an offshore location the jacket structure 1 comprises several legs 10 interconnected by a plurality of braces 11 and is held in place in this example by piles 2 driven into the sea bed 3 the jacket structure 1 serves to support a wind turbine 4 in a deep offshore location for example in water depths exceeding 40 m the wind turbine 4 itself can be quite large for example about 80 m in height with a rotor diameter in the range of 100 140 m particularly when housing a powerful generator in the megawatt range to provide the necessary structural stability the jacket structure 1 can be made of steel legs and braces securely fastened to each other at nodes along the legs the largely u2018 empty u2019 structure therefore presents a relatively small surface area to the forces acting on it above and below the water level fig2 shows a jacket assembly guide 5 according to an embodiment of the invention here the jacket assembly guide 5 comprises four supporting towers 51.