Facade / Opening base
Sill
/sɪl/noun
From Old English syll, a threshold or base.
Definition
The horizontal member at the base of a window or door opening, shaped to shed water away from the wall below.
Fig. 53 — Sill: schematic studyNOT TO SCALE
Illustrative study — Sill · AI-generatedSAMPLE IMAGE
Photo study — Sill · AI-generated00:06
Structural & construction notes
External sills slope outward with a drip groove on the underside. End joints and the junction with jambs need sealing; projecting sills require support and weathering detail.
An educational reference. Project-specific design requires professional guidance.