Final answer:
The term for the vertical blocks with two vertical grooves separating metopes in a Doric frieze is 'triglyphs'.
Step-by-step explanation:
The vertical blocks that separate the metopes in a Doric frieze and typically have two vertical grooves or glyphs are known as triglyphs. In the context of a Doric entablature, the frieze is decorated with alternating panels of these triglyphs and metopes. The triglyphs are decorative panels with three vertical divisions that recall the head of wooden beams from earlier temple constructions, and they give the panel its name. The metopes are square spaces that often contain painted or sculpted decoration, depicting mythological or historical scenes, contributing to the cultural significance of the architectural work.