I have a shell but no nut, and must be broken to be useful.

I make two people out of one. What am I? Solve the riddle → If a rooster lays an egg on the roof of a house, which way does the egg roll? Solve the riddle → What goes over the water without moving? Solve the riddle → What can you hold in your right hand but never in your left? Solve the riddle → What is always yours, but mostly used by others? Solve the riddle →