Asymmetric and/or loculated hydrocephalus can be treated with endoscopic septum fenestration to avoid or to simplify a shunt (1,2). In asymmetric lateral ventricles the septum pellucidum is dislocated to the opposite side and may even be in contact with the lateral wall of the contralateral ventricle (i.e., the thalamus). Perforating the septum with a catheter or a laser beam may damage the underlying tissue. The authors show a safe perforation technique: the septum is pulled towards the tip of the endoscope to enlarge the underlying space. Now the catheter can perforate the septum without the risk of damage to the underlying tissue.