During Surgical procedure, sterile Surgical drapes are used to cover all of the patient's body except for the head and the surgical site or at least a wide area surrounding the operating field; the drapes are clipped to a pair of poles near the head of the bed to form an "ether screen", which separates the anesthetist/anesthesiologist's working area (unsterile) from the surgical site (sterile), that keep the non surgical site of the patient and the operating-table clean and out of infected.