Fashion designers are always looking for a new way to make a neckline in a top or dress, and one way they can do this with the keyhole neckline. This neckline may be fashioned in a couple of different ways, but may be a simple slit in the neck of a blouse or dress. The split is usually, although not always, secured at its top with a hook and eye or loop and button. This kind of neckline is easy to make when sewing a garment, since the sewer only needs to finish the edges of the slit and secure it at the top. Most easy sewing patterns that include a "keyhole neckline" refer to this style.
The second, more complicated keyhole neckline looks more like its name. It is a circle or oval shape cut out of the neckline of a dress or top and secured, usually with a button and loop at the top. A circle or oval is difficult to cut properly, and the material must be well-marked for the cutout to look right.
This style of neckline has been around for some time, but was most popular in the 1940s. It has been used on swimsuits, evening wear and a host of other garments. The keyhole must be well-placed in the garment so it will be attractive. When the opening is placed too low, or is opened too wide, a woman may show more of her decolletage than she intends. It is mostly meant to be a different neckline, not a revealing one. Of course, if revealing is what the wearer wants, a large, low keyhole neckline will serve the purpose. This style was popular in the disco era of the 1970s and was meant to reveal cleavage — and a lot of it.
A keyhole neckline can add interest to an otherwise routine jewel neckline. It is flattering on most women and is usually an attractive feature of a top or dress.