A collar stay is a small piece of plastic or metal, that is fitted specifically into the edges of a dress-shirt collar. It is used to create the illusion of a stiff, crisp collar, and prevents the edges from curling up or down. A collar stay is typically used in dress shirts for formal wear with a jacket and tie. In some instances, it can be sewn into more casual shirts, if the collar is large enough.
How to Use Collar Stays
Purchase a shirt that has a small stitched channel on the underside of the collar leading to the points. This will ensure that collar stays can be used and you don't have to have a tailor sew in the stays for you.
Measure the channel length and width to determine the size of the collar stay you will need. Measure the tip, or pointed end of the channel leading to the edge of the collar, to ensure the the stay you buy will fit properly.
Determine the type of stay that meets your personal preference. Collar stays are made from many different materials and strengths including brass, stainless steel, sterling silver, horn, mother of pearl, or plastic.
Insert the collar stay, pointed end first, into the channel on the underside of your collar. Ensure that the stay fits securely, and end of the stay fits tightly into the corner of your collar.
Ensure that the rounded edge of the stay is short enough so it does not interfere with the crease of your collar. Fold the collar back and adjust the stay, if needed, to keep your collar from curling.