The Army's greatest invention. Small and light to carry around. Faster than a normal can opener if the user has sufficient experience. Also known as a John Wayne, so named because the actor was shown in a training film using it. The P38 can opener is a small folding blade used to open canned rations (such as K-rations or C-rations) amongst many other uses. List of p38 uses were written by the pentagon. MIL-J-0837. Black Colored. US military p-38 can opener. Dimensions: 1.5" x 5/8" (inches), tip extends .5".