In the finite element analysis world, the reuse of common components has long been available with the Parts and Instances method. However, this method has not been available in Nastran. This method is now available in Nastran and is called the Modules method. One of the novel features of Modules is that a Module is a stand-alone input file segment. It has its own definition of nodes, elements, material properties, element properties, loads and boundary conditions. It is a complete and ready-to-run input file segment and is supported in all Nastran solution sequences. It is easy to fully check out each Module before it is used in an assembly. Another novel feature of Modules is that they are designed to be connected automatically. Based on a search tolerance method, Modules can be automatically connected at coincident grid points. This automatic connection feature makes it easy to connect Modules, and is especially useful for reconnecting Modules after they are copied and repositioned. Nastran FEM components are typically organized as include files in an assembly model. Due to the strict requirement of unique entity IDs, common component models cannot be easily reused. In order to be reused, the model needs to be renumbered. This process is not only prone to error, but also means more work for the structural analysts. Modules eliminate the need to renumber. A Module is an encapsulated component model. Entity IDs are not required to be unique across Modules. This means each Module can have its own full range of IDs starting from node 1, element 1, material 1, etc. A Module can therefore be easily dropped into different design variants without the need to renumber. Modules can be easily instanced (copied, translated, mirrored and rotated) to allow them to be reused. Simple Nastran commands are used to create instances. These instance commands are fully supported in the Apex pre-processor. And Modules results are fully supported in the Apex post-processor. Modules results can be displayed individually or as an assembly. A component model may appear in many design variants with thousands of load cases. It is not a trivial task to envelope and max/min search the loads associated with a component. Modules are designed to speed up this process. Nastran can place the results of individual Modules into individual HDF5 files. And additional results for a Module can be concatenated to the existing HDF5 file, making the results post processing much easier and less prone to error. This paper will use several real-world examples to demonstrate the major features of Modules. These examples include an offshore wind turbine platform, a truck frame assembly and an UAV drone model.