Final answer:
The metal plate with rows of pointed needles used to blend or straighten fiber/hair during a hair addition service is called a hair blending plate or a hair addition plate.
Step-by-step explanation:
The metal plate with rows of pointed needles used to blend or straighten fiber/hair during a hair addition service is called a hair blending plate or a hair addition plate. It is an essential tool in the hairdressing industry for creating a seamless and natural look when adding hair extensions. This plate allows the stylist to carefully blend the client's natural hair with the added hair for a cohesive and undetectable result.