Corset busks that open have been around since the mid 1800's. Made of metal an opening corset busk consists of two parts; one side has knobs and the other loops. When the loops are hooked over the knobs the busk acts like a clasp to hold a corset shut. This means that you can get into a corset without someone to dress you. Always loosen the corset laces before attempting to get into and out of the corset. Since a corset is essentially smaller that your body, trying to put the corset on without loosening the corset laces will be impossible and trying to take the corset off without loosening the ties will potentially damage the busk.
You have choices when buying a busk. The most common busk is a "regular busk" or "straight busk" which is white with silver coloured knobs and loops. More colour options have become available in the last few years so you can now get "gold busks" that have gold knobs and loops, "antique brass busks", "black busks" and even ones that have "diamonds"/clear crystals set in the knobs that are called "diamond busks" (though no, they are not real diamonds). Having colour options means you can co-ordinate the busk to the fashion fabric.
There are also "wide busks" and "spoon busks" both of which are silver in colour and made from stainless steel. The "wide busks" are extremely supportive and a good choice for women or men needing/wanting more support - they don't flex nearly as well as a regular busk so they don't curve over the chest well. The "Spoon busk" is historically accurate for corsets of the late 1800's and the bowl of the spoon is meant to cup the stomach...not the chest!
The busk (regardless of style or colour) should be put into the corset with the loop piece on the right-hand side so that the wearer can pull the loop section with their right hand while holding the left side in place. Hooking the loops over the knobs.
Busks can be found in many lengths from 4" to 18" so you can likely find one for any project you have.
The link below will take you an article about getting into and out of a corset with an opening busk.
The next link will take you to a wide selection of articles related to costume making
and the last link will take you to a web page to see all the busks that Farthingales offers for sale