STL Import for SolidWorks is a Stereolithography (.stl) file import add-in for SolidWorks?. This add-in gives SolidWorks the ability to import geometric data from ASCII and Binary STL files. STL Import for SolidWorks reads polygon mesh data stored in STL files. A polygon mesh in a STL file is comprised of a set of triangular faces. STL Import for SolidWorks creates trimmed planar surfaces for each triangle and knits them together.