The present invention relates to an assembly of two structural parts of a wind turbine wherein the structural parts are to be connected in a flange-to-flange connection by a number of bolts and such that a flange of the first structural part and a flange of the second are centrally and rotationally aligned whereby a first borehole in the flange of the first structural part is matched and aligned with a corresponding first borehole in the flange of the second structural part. The structural parts may for example be a tower section or a foundation section. The assembly further comprises a firstand a second rotational guide member releasably attached to each of the flanges of the structural parts. Each of the rotational guide members comprises a U-shaped or L-shaped structure of a first legportion and a second leg portion connected by a central portion, the first leg portion ending in a positioning portion shaped to be inserted into a borehole of the flange, and the second leg portion comprising a stop member, and for at least one of the rotational guide members the structure comprised in the rotational guide member is U-shaped. The stop member of the first rotational guide member is configured for abutment to the second leg portion of the second rotational guide member when the flanges of the first and second structural parts are centrally and rotationally aligned. The invention further relates to a method of positioning and connecting two structural parts of a wind turbine as described above. The method includes first centrally aligning the structural parts with the flanges face-to-face and then rotating the structural part relative to each other until the rotational guide members come into contact with each other.