If you not understand its normal, my English not awesome
You're not using any hack or bug or something like that . Just doing simple knifing with left mouse button. But not hold it, click it many time. If you press too fast it will attk like holding lmb.So dont click soo fast. If u try too much times , you will do that easly. Its not knifing very fast like knife hack but its works too
I hope you understand...(I found it today xD)