Abstract: The surgical knife of the present invention includes a substantially cylindrical housing which has an external housing surface and one open end. A planar knife blade is support for axial movement within the housing so that one end of the knife blade can be extended beyond the open end of the housing. Means, which are well known in the art, are carried by the housing and connected to the knife blade to cause movement of the knife blade in an axial direction for extension beyond the open end. A raised surface is provided on the housing which has a cross section dissimilar to the cross section of the housing for use in preventing rotation of the knife to thereby orient the knife blade along a desired plane when the knife is supported on a surface. One embodiment of the surgical knife provides for the dissimilar cross section to be a square with four flat surfaces so that these surfaces can rest in a complimentary groove in a supporting tray of a knife blade setting device.