Answer:
What you do to determine the length of something
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.
Mouth up it gets filled, mouth down it gets empty.
I always run but never walk, I sometimes sing but cannot talk, No head on which a hat to place, You always look me in the face.
When a doctor hits you with a hammer he is testing this
I am a room that has a roof but no walls. What am I?
Easy
Animal
Difficult
Food
Funny
Kids
Logic
What am I?