NOVELTY - The system (1) has positioning units for positioning a work platform (20) near a part of an off shore structure, where the positioning units mount the work platform onto a main platform (10) to be situated at a water level (W) and lift the work platform relative to the main platform. The positioning units comprise leg pieces for forming a tower onto the main platform and attaching unit for attaching the work platform to the tower and a lifting unit for lifting the work platform along the tower. The work platform comprises a crown for attaching the work platform around the tower leg pieces.    USE - System for facilitating work e.g. light work such as painting or performing small repairs, and heavy work such as replacement of parts e.g. rotor blades or head of nacelle, to be performed on a part of an off shore structure e.g. wind turbine, situated above water level. Can also be used for an off shore structure such as long bridge and drilling platform.    ADVANTAGE - The leg pieces require less space than an entire leg, and can be transported on a deck of the main platform. The tower to be formed out of the leg pieces allows stable attachment of the work platform and allows the possibility of lifting the work platform along the tower. The system can be used even at high wind speed and/or high waves in a safe manner. The combination of the main platform and the work platform provides necessary stability to operate in rough weather under safe conditions. The work platform is not connected to the off shore structure, and can be positioned independently relative to the off shore structure, thus allowing the work to be performed on the entire off shore structure. The system can accept greater loads by adopting the combination of the main platform and work platform, thus allowing replacement of parts such as entire rotor blades or head of nacelle even with blades.    DETAILED DESCRIPTION - The main platform comprises a jack-up rig or pontoon like structure. An INDEPENDENT CLAIM is also included for a method for installing a system for facilitating work to be performed on a part of an off shore structure situated above water level.    DESCRIPTION OF DRAWING(S) - The drawing shows a side view of a system for facilitating work to be performed on a part of an off shore structure situated above a water level in transport position.    Water level (W)    System for facilitating work to be performed on part of off shore structure (1)    Main platform (10)    Supporting legs (11)    Drive (12)    Jack-up system (17)    Work platform (20)