A busk is the rigid element of a corset

Corset

A corset is a garment worn to hold and shape the torso into a desired shape for aesthetic or medical purposes...

 placed at the centre front.

In stays

Bone (corsetry)

In corsetry, a bone is one of the rigid parts of a corset that forms its frame and gives it rigidity.-Purpose, history and materials:The purpose of the boning in a corset varies slightly from era to era....

, the corsets worn between the fifteenth and eighteenth centuries, the busk was intended to keep the front of the corset straight and upright. It was made of wood

Wood

Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

, ivory

Ivory

Ivory is a term for dentine, which constitutes the bulk of the teeth and tusks of animals, when used as a material for art or manufacturing. Ivory has been important since ancient times for making a range of items, from ivory carvings to false teeth, fans, dominoes, joint tubes, piano keys and...

, or bone

Bone

Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

 slipped into a pocket and tied in place with a lace called the busk point. These busks were often carved and decorated, or inscribed with messages, and were popular gifts from men to their sweethearts.

In the middle of the nineteenth century, a new form of busk appeared. It was made of two long pieces of steel, one with loops and the other with posts, that functioned in the same way as hook and eye fastenings on a garment http://www.farthingales.on.ca/busks.php. This made corsets considerably easier to put on and take off, as the laces did not have to be loosened as much as when the corset had to go over the wearer's head and shoulders. The second half of the nineteenth century also saw the invention of the spoon busk

Spoon busk

The spoon busk was a specialised kind of busk -- the rigid element of a corset placed at the centre front. As its name implies, it was shaped like a spoon, with the bottom part of the busk widening and taking a dished form...

.