Lexicon
Eyebrow

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Formed when the thatch is swept up in an arc over the entrance, thus allowing a full-height doorway to be fitted into a lower side wall. Even when the side wall is high enough to accommodate a normal doorway the thatch is often lifted in an eyebrow to form a gable over a fanlight or small dormer window, when it is referred to as an eyebrow dormer or a leg mutton or leg’o mutton gable [see also wolweneus gable].

(Walton, 1995: 125)