In the restoration of wooden wind instruments, the type of damage must be considered. There is damage due to use from the humidity of breath, and mechanical effects. There is damage connected with weak points in the construction. Finally, there are inherent properties of the materials such as corrosion of metals or shrinkage of the wood. Cracks in the wood are frequently encountered. Components of the instruments are normally connected by wooden rivets, which often show signs of decay or become loose.