ferrule (of a cane, umbrella, etc.); butt end (of a lance, pike, etc.)
hard tip (of a mushroom stem)
杖の石突きが擦り減った。
The ferrule of the cane wore down.
傘の石突きを店で交換してもらった。
I had the umbrella's ferrule replaced at the shop.
武士は槍の石突きを磨き、その輝きを確かめた。
The warrior polished the butt end of his spear and checked its shine.