The manual or semi-automatic preparation of triangular and tetrahedral meshes for simulations is a very time-consuming task. The mesh preprocessing software MERGE however masters this task fully automatically and in a considerably shorter timeframe. It takes CAD or STL data as input, repairs invalid meshes and connects them together. The small gaps between the input objects are automatically closed and even glancing intersections can be cut off. The output can be supplied in different variations, either as a mesh that minimizes the number of elements, as a mesh consisting of high-quality surface triangles, or as a conforming tetrahedral mesh, while all of these possibilities are suitable for CFD or CAE simulations. Connecting the meshes of an entire car body can be done in (as little as) a few hours and does not require any manual work.