Tie bar (also known as “Tie Slide”) is a fashion accessory that serves to hold the tie in place. Its task is mainly to prevent a tie from falling into the soup or fluttering in the wind.
Do not confuse a Tie Bar with a Tie Clip because their construction is a little bit different: Tie Bars slide over the tie and shirt to help secure the tie to the shirt, while Tie Clips open with a jaw on a spring to close around the tie and the shirt.
Tie bar is placed on a tie between the third and fourth buttons of the shirt. A typical mistake is in choosing a tie bar which is too wide: the clip should not stick out beyond the edge of the tie and should even be slightly narrower than the tie itself.