Method for assembling two wall formworks (12, 13), wherein the two wall formworks (12, 13) comprise a formwork skin and supporting elements for the formwork skin, comprising the steps of: a first locking device is attached to the rear side of the one first wall formwork before this first wall formwork is erected, the first locking device has a pipe section which, in the fastened state, extends into the one first wall formwork, at least as far as the formwork skin, the two wall formworks (12, 13) are placed opposite each other, an anchor rod, which is partially encased by a displaceable arranged sleeve and can only be partially encased, is pushed through anchor rod bores of the two wall formworks (12, 13) in such a way that one end of the sleeve rests against the end of the pipe section which extends into the first wall formwork, the end of the anchor rod which is not pushed through is firmly connected to a second locking device in such a way that a pipe section of the second locking device extends into the second wall formwork, at least as far as the formwork skin of the second wall formwork and adjoins the sleeve, wherein the sleeve is formed of a tube made of plastic and two end pieces, characterized in that, each end piece being detachably connected to a respective end of the tube, in that an insertion portion of the respective end piece can be inserted into the tube of the sleeve, wherein the outer diameter of the sleeve corresponds to the outer diameter of the pipe sections, so that one end of the sleeve can be sealingly adjacent to one end of a pipe section, wherein the maximum outer diameter of each end piece is equal to or at least substantially equal to the maximum outer diameter of the tube. a first locking device is attached to the rear side of the one first wall formwork before this first wall formwork is erected, the first locking device has a pipe section which, in the fastened state, extends into the one first wall formwork, at least as far as the formwork skin, the two wall formworks (12, 13) are placed opposite each other, an anchor rod, which is partially encased by a displaceable arranged sleeve and can only be partially encased, is pushed through anchor rod bores of the two wall formworks (12, 13) in such a way that one end of the sleeve rests against the end of the pipe section which extends into the first wall formwork, the end of the anchor rod which is not pushed through is firmly connected to a second locking device in such a way that a pipe section of the second locking device extends into the second wall formwork, at least as far as the formwork skin of the second wall formwork and adjoins the sleeve, wherein the sleeve is formed of a tube made of plastic and two end pieces, characterized in that, each end piece being detachably connected to a respective end of the tube, in that an insertion portion of the respective end piece can be inserted into the tube of the sleeve, wherein the outer diameter of the sleeve corresponds to the outer diameter of the pipe sections, so that one end of the sleeve can be sealingly adjacent to one end of a pipe section, wherein the maximum outer diameter of each end piece is equal to or at least substantially equal to the maximum outer diameter of the tube.