An invasive device in the form of a thin, rigid rod intended to provide guidance for exchanging one endoscope sheath, which has been introduced into a patient, for another (e.g., exchange a transvaginal diagnostic sheath with an operative sheath). It is intended to be inserted into the lumen of the initial sheath to guide sheath retraction and remain in situ to guide replacement sheath introduction; the guide is removed once the replacement sheath is in place. This is a reusable device.