There are two main types of fibre needles, Thorn needles and Bamboo needles. Both are basically hardened wooden needles that can be re-sharpened after playing.
Bamboo needles usually have a triangular cross-section and need a suitable hole in the sound-box to fit. These are sharpened by cutting off a slice at the end of the needle to produce a new point. Thus can be done with a craft knife but there are patent cutters available to do the job efficiently.

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Thorn needles have a round cross-section more like regular steel needles and can be re-sharpened with an emery board or a patent sharpener. Two of these are the IM and BCN models.

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Please note that steel needles cannot be re-sharpened.