A cylindrical helix is just a spiral on a cylinder, like an ordinary spring or the thread on a bolt. There are two kinds, a right-handed helix and a left-handed helix and in the case of a bolt one has to be turned clockwise to screw it down and the other anti-clockwise. If I turn a left-handed helix over (top to bottom) does it become a right handed helix? Give as simple an explanation as you can.