An instrument for guiding a rod into a receiving area of an implant includes a coupling unit for coupling the instrument to the implant, a rod provided with an outer thread that can be positioned axially relative to the coupling unit, and at least one inner threaded segment arranged in an axially fixed manner relative to the coupling unit that can be brought into engagement or out of engagement with the outer thread of the threaded rod. The threaded rod has a stop, and the instrument has a locking element which is arranged in an axially fixed manner relative to the coupling unit for interacting with the stop. The locking element can be positioned in a radial direction relative to the threaded rod and is pretensioned in the direction of the threaded rod to engage with the stop by a pretensioning element which applies a radial force.