DO YOU KNOW ME?

I am a little thing with a big meaning.
I help unlock doors, open hearts, dispel prejudice.
I create friendship and good will.
I inspire respect and admiration.
Everybody loves me. I bore nobody.
I violate no laws. I cost nothing.
Many have praised me, none has condemned me.
I am pleasing to those of high and low degree.
I am useful every moment of the day, in many ways.
I am called “COURTESY.“