Abstract: An improvement is provided in an apparatus which is adaptable to be run within a subterranean well for the setting and locking of a locking module within the profile of a complimentary landing nipple carried on a conduit within the subterranean well. The improvement comprises a longitudinally extending probe means carried by the apparatus at one end. First receiving means are exteriorly defined on said probe means for selective receipt of a lock control member of a lock control means and for shifting of the lock control member to one of two positions. Second receiving means are provided on a locking module for selective receipt of the lock control means. Means on the apparatus are provided for shifting the lock control member to the other of the two positions while the lock control means is maintained in the receiving means. Use of the apparatus assures proper engagement of the locking module within the landing nipple profile prior to retrieval of the apparatus from within the well.