In the catalogue of a tool supplier, I just found this great invention: an adjustable double bass soundpost. This soundpost offers exact adjustment of the soundpost length, even from the outside of the bass. No need for using two soundposts for summer and winter seasons anymore. And it’s easy to use for both players and luthiers.
Update: Somebody just clarified that this tool is rather a guitar repair tool than an adjustable double bass soundpost. Sorry for the above incorrect information. My fault 😉