A simple trick can do the job! I’m lean myself but I could cut a coir twine easily..If you wish to try, here are the steps.
(sorry about the bad English, it gets difficult to explain things in English)
1. Wind one end of the thread to your left hand thumb, as shown in the pic.
2. Now, let the rest of the thread on your palm in shape of U
3. The other end of thread(the right portion of thread that makes U shape) should go around your the palm, traveling on the dorsal hand, and come back on to palm from the bottom to get into the U shaped thread from inside.
4. Now, just pull the other end of thread downwards with your right hand, and to your magic, the thread is just cut at the lower edge of U!
Caveat: I’m not held responsible if something goes wrong( other than the thread cutting into half, though 🙂 )!