It's definitely not a telltales, can't even say it's a belief but..... I wanted to post it here so here we go.

Even since I was a little girl, until now,  my parents had thoght us to throw salts on the door whenever we heard a knocking on the door, and no one's in there.

Have you experienced this?! Yeah, I do. And surely my dad and mom had experienced one too even back in P.I. (Philippine Island). Did you opened the door and find nobody's really there?! Did it creeped you out?!

Here's what to do,  when you heard a knocking on door, don't just open it. I remember my parents told me that "real people" knock three times on the door. It is weird hearing just a one knock on your door, right?! or two?! And when you opened the door and saw nobody's there and this gives you a creep or ghost bumps, throw  some salts in there. (Just make sure, you're not playing with your kids around, or your neighboors kids, this, makes it a different case.) I don't know why it is suppose to be done or how it work out. I didn't ask, and I don't wanna ask.