Using medium consistency white royal icing fitted with round tip 12, pipe a line to desired length of the trim.
Use medium consistency red royal icing fitted with round tip 5. With light pressure, overpipe with 2 diagonal lines evenly spaced apart. Then, with heavy pressure, pipe one additional wider diagonal line after the double thin lines, evenly spaced apart.
Repeat piping additional diagonal lines, alternating between two thin lines using light pressure and one wider line using heavy pressure.