Extra Eyelets on Running Shoes
Most shoelaces aren't long enough to even reach the extra eyelets up by the ankles, so what are they for? They're meant to create a breathable fit and help avoid chafing during sports.
Hole on the Back of iPhone
If you don't use a case on your iPhone, you might want to reconsider after this. There's a small hole on the back of the phone by the camera that serves a useful purpose. It's a small microphone that allows your voice to be picked up from all sides of the phone.