Known commonly as Straight Wall, it's official name means "straight fault". It is the best known of all lunar faults. It was once thought to be a vertical cliff, but more recent measurements show it to be a slope, variously estimated at between 15° and as much as 41° (which would still make it one of the steepest slopes on the visible face of the Moon).
Photo: Thierry Legault. The full size original of this and other high definition lunar images may be seen at his High Resolution CCD Imaging site.