Used by sail-makers, are seaming, bolt-rope, or roping needles, all three-sided, and of very fine steel.
The Needles of the Isle of Wight are the result of cracks in the rocks, through which the sea has worn its way, as also at Old Harry, Swanage Bay. As the chalk formation stretches westward, the structure changes in hardness until at Portland we meet with Portland stone. In California many of the needle rocks are of volcanic origin; others again are basaltic columns.