# 4.2.2. Assemblies

Assemblies can be defined within Fuego to aggregate mesh parts (block, surface or node list) together. An example of defining a surface and block assembly is shown below:

    Begin assembly inflow
      surface = surface_1 surface_2
    End assembly

    Begin assembly fluid_blocks
      block = block_1 block_2
    End assembly

This block is defined under the finite element command block. It should be noted that each assembly must contain the same type (or rank) of parts (block, surface or node list). Building upon the examples in Mesh Part Material Assignments, we can increase the readability of our input deck by doing the following:

    Begin assembly fluid_blocks
      block = block_1 block_2 block_3 block_4
    End assembly

    Begin Parameters for Block fluid_blocks
      material air
    End

Assemblies can be used in a variety of operations (i.e. boundary conditions and postprocessing operations) and generally help readability of an input file. In addition, these assemblies can be used for transfers to other apps as well. The preferred method for grouping mesh parts together within an input deck is through assemblies.

A summary of commands available for defining assemblies is located in Finite Element Model.