In older instruments, it is not uncommon for the blocks to have a crack. It is important for structural integrity for this to be replaced. In addition, ribs often need to be trimmed, and this can be done at the same time.
A common procedure done in the process of restoration, is installing a new bass bar, if the old one has a problem, or is not fitting properly.
This is a necessary repair when a crack forms under or near to the soundpost area. Prior to excavation of the patch area, a negative plaster cast must be made, to create a safe working/clamping medium