A locking device assembly or twistlock assembly for mounting into a lifting beam or spreader, for releaseable coupling to a container having at its top side corner castings incorporating oval openings. The spreader (2) has rotatable twistlocks (20) with oval locking heads (6) which in their open position (A) can be inserted into said openings and after being rotated approximately 90 degrees to a locking position (B) secure the corner castings to the twistlock heads (6) thereby coupling together the container and the spreader. Each twistlock (20) is mounted in a bearing house and is rotated by an operating device (5) which is releasably connected to a turning element (17) surrounding the end part (14) of the twistlock (20) and demountably but unturnably affixed to the twistlock (20), e.g. by a key (18). Each twistlock (20) below the end part (14) has an annular groove (13) for insertion of removable bearing elements (15, 16), e.g. a split bearing ring, forming a stop to the bearing house (3) of the twistlock for fixation of the shaft (20) to axial displacement at lifting. The turning element (17) is arranged to keep the bearing rings (15, 16) in their position in the groove (13) and also arranged to be fixed to axial displacement by interacting means (22-25) acting between the turning element (17) and its fixed surrounding parts, in the first place the bearing house (3), in such a way that the element is fixed axially at rotation within the working area (A-B), i.e. from the open position (A) to the locking position (B) and vice versa, but is released axially for freeing and removing the bearing rings (15, 16) at rotation outside the working area.