Purpose: A tie bar is meant to keep your tie fastened to the placket of your shirt. It sounds obvious, but bears repeating lest a perfectly fine tie bar be attached only to a tie and simply left to swing in the breeze.
Styles: Tie bars come in two styles: pinch clasp and slide clasp. In general, I prefer a pinch clasp as I find it holds the tie more securely and stays in place better. However, if you have a thin tie, a slide clasp may be more appropriate as many pinch clasps are made to secure thicker fabrics and may not lay flat in that situation, making the clasp visible.
Size: A tie bar should never be wider than your tie. It should range in size between one inch and the width of your tie. 3/4 the width of the tie is just about perfect.
Placement: A good rule of thumb is to fasten the tie bar between your third and fourth buttons, around the sternum, and just below the pectoral muscles.
Detail: Just before fastening the tie bar, pull your tie upward to blouse it slightly. This will add a nice bit of depth and visual appeal and will also keep you from feeling constricted or like the tie bar is holding you in place.
Angle: Always wear the tie bar perpendicular to your tie; never at an angle.
Color: You can’t go wrong with silver. It’s classic, matches almost anything, and looks great on everyone. But if gold is your thing or you’re wearing gold accessories, then go for it: it’s always best to make sure your metals match. Avoid colorful tie bars; it will just look like you are trying too hard. As with most menswear details, a tie bar should be an accent, not the topic of conversation.
Bonus Tip: A tie bar should not be worn with a waistcoat or cardigan. Remember, the purpose of a tie bar is to hold the tie in place. If you are wearing a waistcoat or cardigan that’s already taken care of and at that point, a tie bar just becomes unnecessary and redundant.