First the mask is submerged in hot water (a). Then a hole is widened for the animal’s nose and mouth to enable breathing (b). Next the mask is stretched and molded over the sedated animal’s head while she is propped up in the chair used during experiments (c). After cutting holes for the monkey’s eyes, nose, and mouth, the mask is placed on the awake animal’s head for day-to-day use as shown in (d), (e), and (f).