A process to fill in the gaps and spaces with pieces of thin, tapered material between parts that make up a plane's fuselage to make them fit properly. Improperly joined pieces can cause the parts to fail prematurely as a result of a reduced fatigue life. Compared to metals, modern composite materials are especially susceptible to incorrect shimming due to reduced malleability which causes stress to build up and eventually lead to delamination. Shimming problem is a manufacturing quality issue that may require inspections and repairs of the aircraft.