Answer:
Gets rid of bad ones, short and tall. Tightens when used, one size fits all.
Runs smoother than any rhyme, loves to fall but cannot climb.
Whoever makes it, tells it not. Whoever takes it, knows it not. Whoever knows it, wants it not
What measures out time. Until in time all is smashed to it?
We are five little objects of an everyday sort. You will find us all in a tennis court.
What is so fragile that saying its name breaks it?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?