糸 and 針: thread, needles, and clock hands
Distinguish sewing material and tools from a needle-shaped item in another context.
Thread for sewing
糸 (いと) means thread. 「白い糸で縫いました」 means sewing with white thread.
「糸を短く切りました」 says the thread was cut short. 短く describes the resulting length.
A needle that takes thread
針 (はり) means needle. 「針に糸を通しました」 means threading a needle.
「針を箱に戻しました」 says the needle was returned to the box. Do not change the returned object from 針 to 糸.
針 in a clock context
「時計の針が止まっています」 says the clock hands have stopped. It does not put a sewing needle inside the clock.
「長い針と短い針」 refers to the long and short hands in a clock context. Use a clue such as 時計 to identify the kind of 針.
Is 「時計の針」 a needle used for threading?
Show the answer and why
No. It is a clock hand that indicates the time.