The above illustration shows the David Kopf model 900 Student Stereotaxic Instrument.
The Stereotaxic Instrument can be divided into two parts: the "head holder" and the "electrode carrier". The head holder includes the base plate and the horseshoe shaped parrt which includes the "ear bars", "incisor bar" and "nose clamp". The function of the head holder, as the name suggests is to immobilize the rat's head and orient it to the correct angle for surgery. The electrode carrier includes the electrode holder and 3 calibrated drives. The AP drive moves the electode holder in the Anterior Posterior plane. The DV drive moves the holder in the Dorsal Ventral Plane and the ML drive moves it in the Medial Lateral plane. Each of the drives has a vernier scale to allow for precise positioning of the electrode.