Humidity cracks often go through post positions or metal inserts.
There are three scenarios when you can get cracks inflicted by dryness. They are rare and always involve metal parts, which are mounted into the wood. Most of the time, these are posts sometimes the register tube.
1. if the mechanism of the instrument was added before the wood was properly dried. When the instrument dries further, the wood will shrink and the metal posts are an obstacle that can cause the wood to crack. In particular, if the instrument gets sent to very dry areas like Montana in the Winter with -40 C and zero humidity or Arizona in the summer with 35 C and no humidity, you might experience cracks, even without having played the instrument.
2. exposed to extreme heat, such as inside a car or behind a window in the sun. Now the metal can expand while the wood remains in its original dimension. This can also result in cracks at the posts. Always be sure to keep your instrument inside the cabin if you drive in extreme weather and keep the instrument in a humid environment. Humidifiers, like the Dampit, can do miracles and are a great investment.
3. older Buffet clarinets had a conical register tube. If they were pressed into hard or while the instrument was very humid, they can cause cracks as well. When they are removed or exchanged it is best to install them with a soft and elastic thermo-glue.
Don't get the instrument pinned under any circumstances!!! (Read also: Crack pinning]