Dirtlib: a library to add an overset capability to your flow solver. The modifications to a flow solver to add an overset capability can be an impediment to developers wishing such a capability. The Donor interpolation Receptor Transaction library (DiRTlib) is a solver neutral library that simplifies the addition of an overset capability to a flow solver by encapsulating the required operations. This paper discusses the design issues of such a general capability and details the use of DiRTlib in a solver.