Masonite and Hardy plank are two different materials. Take a piece off the wall and go to a building supply store to match the profile. Hardy plank comes in smooth and textured, like a wood grain and I believe different widths. You can usually rent a cutter from the supply house which will make your life 10X easier when cutting the pieces cleanly. This shouldn't be a difficult installation, just make sure to stagger your seams like you would with a hard wood floor. Masonite is like a pressed cardboard and doesn't hold up well exposed to the weather. hardy plank is a cement type material and preforms better. Get a installation sheet so you can follow the recommended nail pattern.