Abstract: A portable tool for forming louvers in a sheet metal work piece. The tool has a substantially C-shaped frame with an upper leg, a lower leg, and a body forming a throat in which the louvers are formed. A female die assembly is mounted on the lower leg of the frame. A male die is positioned in a carriage which slides longitudinally along the upper leg of the frame. Stops define the length of travel of the carriage and clamps hold the work piece between the female die assembly and the male die. An increasing cutting and forming force is applied to the male die, and against the work piece and the female die assembly, until a louver is cut and formed in the work piece.