finial

noun3

1. •
   Especially in Gothic architecture: an ornament, often in the form of a bunch or knot of foliage, on the peak of the gable of a roof, a pediment, a pinnacle, etc.

   • His [Butades'] invention it vvas to set up Gargils or Antiques at the top of a Gavill end, as a finiall to the crest tiles, vvhich in the beginning he called Protypa. — 1601
2. •
   Any decorative fitting on the corner, end, or top of an object such as a canopy, a fencepost, a flagpole, a curtain rod, or the newel post of a staircase.

   • The finial is also of timber (probably oak) and is of the rather elaborate type, originally favoured by the London & South Western Railway for its timber masts. — 1947
3. •
   [before a noun] (figurative) The completion or end of something.

   • But, as the Phoenix on my Front doth glister, / Thou shalt the Finials of my Frame illustre. — 1608