Decorate roof. Use red and white icings and pipe vertical lines on roof. For wide lines, use white icing to pipe 2 to 3 lines side-by-side, and smooth together with finger dipped in cornstarch. Alternate with wide and narrow lines, piping a red line between two narrow white lines. Use red icing to pipe stripes on wide white lines. Use white icing to pipe zigzags on roof peak and attach candy. Use white icing to pipe icicles along eaves.