Which denominations regulate how a cross is worn on the body?

In public and private, people wear many different crosses in many manners. Which denominations hold any principles, explicit or implicit, that govern the display of crosses on the body? Speculating, such rules might require that the cross touch the skin, or that it never be removed, or that it be hung on the neck and not anywhere else on the body, or that it never be worn by certain persons or in certain situations, or that it must be of certain material to carry.