A medical device holding assembly includes a carrier sheath, which carries an endoluminal medical device such as an embolization coil. The assembly also includes a housing including at least one holding element to hold the sheath, and a fixation device attached to the housing and coupled to the sheath. The fixation device includes a locking element having an unlocked configuration, which allows the sheath to slide relative to the housing, and a locked configuration, which fixes the sheath to the housing. A lock actuator is configured to lock permanently the locking element into the locked configuration. As a result, the sheath with the medical device held therewithin cannot be removed from the holding assembly during the deployment procedure, thereby ensuring that the procedure can be carried out by a single person and also protecting the integrity of the medical device before it is deployed into a patient.