From which also always she is: a protective symbol and warm symbol. If she is from clear material (foil): One would like to differentiate himself, although one is open, besides, for information and cares to it, not 'to lose the view'. Who exposes himself to other (looks), 'drops all covers'. Cover (shell, case) can express as facade that one hides his true being (maybe also from himself). The symbol sometimes points out to the fact that one has not penetrated in a matter yet to the core, itself only even more clarity must get, before one makes, for example, a decision.
(See also facade)