Triglyph on Belsay Hall, Northumberland

Triglyph is an architectural term for the vertically channeled tablets of the Doric frieze in classical architecture, so called because of the angular channels in them. The rectangular recessed spaces between the triglyphs on a Doric frieze are called metopes. The raised spaces between the channels themselves (within a triglyph) are called femur in Latin or meros in Greek. In the strict tradition of classical architecture, a set of guttae, the six triangular “pegs” below, always go with a triglyph above (and vice versa), and the pair of features are only found in entablatures of buildings using the Doric order. The absence of the pair effectively converts a building from being in the Doric order to being in the Tuscan order.