Kelim, Chapter Thirteen, Mishnah Five
1) A needle whose eye or point is missing is clean.
a) If he adapted it to be a stretching-pin it is susceptible to impurity.
2) A pack-needle whose eye was missing is still susceptible to impurity since one writes with it.
a) If its point was missing it is clean.
3) A stretching-pin is in either case susceptible to impurity.
4) A needle that has become rusty:
a) If this hinders it from sewing it is clean,
b) But if not it remains susceptible to impurity.
5) A hook that was straightened out is clean.
a) If it is bent back it resumes its susceptibility to impurity.
Section one: If the needle is missing its eye or point it is pure because it cannot be used. However, if he fixed this needle to use it as a stretching-pin (to stretch out canvases or laundry for them to dry), it is susceptible because stretching-pins don’t need points or eyes to be usable.
Section two: A “pack-needle” is generally used to sew packs. However, due to its large size it can be used to write with on wax, and therefore it is still susceptible to impurity even without an eye through which to thread it. But if its point is missing, it is not at all usable and is clean.
Section three: As we learned in section one, a pin without an eye or a point can still be used as a stretching pin. Therefore it is susceptible in all cases.
Section four: A needle which has become rusty is susceptible to impurity as long as the rust does not hinder it from use.
Section five: The hook loses its usability if it is straightened out. Thus it is pure. If he bends it back to make it a hook, it is again susceptible to impurity. The Rambam explains this line as meaning that it returns to its original state of impurity, as is the rule with metal vessels that are broken and then fixed (see 11:1).