Abstract: Mould assembly including a first mould part (2) and a second mould part (4) for moulding a substantially elongated, closed profile member, in particular a wind turbine blade of fibre-reinforced polymer, said mould assembly including a hinge mechanism (6) with a hinge line (7) extending parallel to the two mould parts in the longitudinal direction of the mould to allow turning of the mould parts in relation to each other between an open position and a closed position. The mould assembly includes displacement means for a rectilinear translational movement of the second mould part (4) between a partially closed position and a completely closed position. The displacement means are formed of guide rods (8) including drive means for displacing the guide rods (8) and thus for moving the two mould parts between the partially closed and completely closed positions. The invention further relates to a method of using the mould assembly.