Woodworm damage is a common problem in old instruments. We often only see the exit-hole from the worm that lived in, and ate its way through, the wood for up to 4 years. The use of CT scans allows us to analyse the damage thoroughly. The worm damage has to be completely plugged and supported with patches. The most modern restoration techniques work with a CNC milling machine which follows the worm tracks and creates a patch so precise that it can be glued in one piece.