Cross necklaces like seatbelts.
The sign of Jesus Christ our lord and savior, the cross has become a Christian symbol of hope, faith, and many dominations of the same religion.
The seatbelt. The sign of safety and common sense. The seatbelt has become the symbol of safe drivers, cautious parents, and conditioning.
I believe these two are related. Christians wear their cross necklaces in almost a symbolic seatbelt. Now they say God has a plan for us all and he will keep us safe from all harm. And this promise reminds me of one not so binding. So long as thou bucklest up, thy drive shall be safe no matter if you crash or not.
Christians use these crosses like a seatbelt in many metaphorical and no literal ways. For both you must put your faith in something that seems so flimsy and while you have heard how they saved others, you aren't too sure how to feel.
And because no matter how much you believe in the seatbelt, there are people that will die with it on.