That is something that I share with the students in my beginner quilting class - needles definitely have a male side and a female side!!! It's much easier to thread from the female side so even when you can't tell by eye, if the thread doesn't go through easily, just turn the needle to the other side. Cutting the thread at an angle helps too. Did you also know that you should knot the end of the thread that you have just cut from the spool, and not the leading edge of the thread?