Collar stays

Collar stays, collar sticks, bones, knuckles, tabs, in the UK, collar stiffeners, and in Eastern Canada collar stiffs) are shirt accessories.

Collar stays are smooth, rigid strips of metal (such as brass, stainless steel, or sterling silver), horn, baleen, mother of pearl, or plastic, rounded at one end and pointed at the other, inserted into specially made pockets on the underside of a shirt collar to stabilize the collar's points. The stays ensure that the collar lies flat against the collarbone, looking crisp and remaining in the correct place. Often shirts come with plastic stays which may eventually need to be replaced if they bend; metal replacements do not have this problem.

Collar stays can be found in haberdashers, fabric- and sewing-supply stores and men's clothing stores. They are manufactured in multiple lengths to fit varying collar designs, or may be designed with a means to adjust the length of the collar stay.

There are also some brands that manufacture metallic collar stays with a magnet for keeping the collar straight and stiff.

A specific collar stay discreetly adds a button hook on one end, to help fasten tiny buttons on dress shirts; e.g. placket, cuffs or button down collars.

Collar stays are removed from shirts before dry cleaning or pressing, as they could damage the shirt in the process, and then are replaced prior to wearing. Shirts that are press ironed with the collar stays are vulnerable to damage, as this results in a telltale impression of the collar stay in the fabric of the collar. Some shirts have stays which are sewn into the collar and are not removable.

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Wikipedia