(n.) A fixed or movable ring, tube, or lining placed in a hole.
(n.) A kind of cap or cover, or sometimes a broad ring, for the end of the finger, used in sewing to protect the finger when pushing the needle through the material. It is usually made of metal, and has upon the outer surface numerous small pits to catch the head of the needle.
(n.) A ring of thin metal formed with a grooved circumference so as to fit within an eye-spice, or the like, and protect it from chafing.
(n.) A tubular cone for expanding a flue; -- called ferrule in England.
(n.) A tubular piece, generally a strut, through which a bolt or pin passes.
(n.) Any thimble-shaped appendage or fixure.