Abstract: An offshore wind turbine blade and tower maintenance devices and systems, more particularly, to the system for service tools positioning relative to the offshore wind turbine blade and tower. An arrangement for lowering and raising service tools used for offshore wind turbine blade and tower maintenance, having: a truss system, a rigging and a rigging pulling in and letting out means. The truss system, includes booms, pivotally attached to a supporting means, which are adapted to be leaned against or releasably fixed to a wind turbine tower or wind turbine tower mooring elements; wherein the rigging and a rigging pulling in and letting out means are operably connected with the truss system, so to allow lowering and raising service tools used for offshore wind turbine blade and tower maintenance.