Design a template ruler to draw hairlines on client's

My project is to design a template ruler that will enable me to draw hairlines on clients' scalps. I am looking for someone who has a strong background in creating rulers because this is a unique situation and the right design is important. In order to ensure the utmost quality and precision, the ruler must be made of plastic and not have any specific dimensions since they will be used for both professional and personal projects. The use of the ruler is both professional and personal, so someone with experience in creating rulers used for both would be ideal. This is an important project and I need the best quality out there. I'm confident in finding a talented freelancer to help me make this ruler a reality.