Method for producing a precast concrete tower segment of a wind turbine tower, comprising the following steps: placing an inner formwork having at least one bore and at least one holding unit on an inner side of the inner formwork in the region of the bore, introducing a removable element at the first end of the concrete anchor from the outer side of the inner formwork through the bore into the holding unit in order to hold the concrete anchor, placing an outer formwork, pouring concrete between the inner and outer formwork (220, 210), removing the removable element in the first end of the concrete anchor, and removing the inner and outer formwork (220, 210), wherein the holding unit is designed in such a way that the removable element is introduced in one direction and blocked in the opposite direction, wherein the holding unit has a spring action when introducing the removable element and a locking action in the opposite direction, wherein the holding unit has two holding plates which are arranged parallel to each other and which are fastened to each other by means of bolts, spacer plates and two holding elements, wherein the holding elements have a first resilient end, a locking portion and a second end, wherein the second end is held by means of two bolts while the resilient end is held by one bolt, wherein the holding plates each comprise two fastening portions at their first ends, wherein a cut out is present between the two fastening portions, wherein the holding plates each comprise a cut out at their second end. placing an inner formwork having at least one bore and at least one holding unit on an inner side of the inner formwork in the region of the bore, introducing a removable element at the first end of the concrete anchor from the outer side of the inner formwork through the bore into the holding unit in order to hold the concrete anchor, placing an outer formwork, pouring concrete between the inner and outer formwork (220, 210), removing the removable element in the first end of the concrete anchor, and removing the inner and outer formwork (220, 210), wherein the holding unit is designed in such a way that the removable element is introduced in one direction and blocked in the opposite direction, wherein the holding unit has a spring action when introducing the removable element and a locking action in the opposite direction, wherein the holding unit has two holding plates which are arranged parallel to each other and which are fastened to each other by means of bolts, spacer plates and two holding elements, wherein the holding elements have a first resilient end, a locking portion and a second end, wherein the second end is held by means of two bolts while the resilient end is held by one bolt, wherein the holding plates each comprise two fastening portions at their first ends, wherein a cut out is present between the two fastening portions, wherein the holding plates each comprise a cut out at their second end. wherein the holding plates each comprise two fastening portions at their first ends, wherein a cut out is present between the two fastening portions, wherein the holding plates each comprise a cut out at their second end.