CAD design package file used by TopSolid, a software solution for managing CAD projects; may store references to part and assembly design documents, bill of materials documents, drawing drafts, and exploded part design documents; used for consolidating and organizing CAD project documents. By default, TOPPRJ files are stored within subdirectories of TopSolid's TopSolidPdm\ directory (which is created by default as C:\TopSolidPdm\). The software's user interface encapsulates access to all project files, so TOPPRJ files are not accessed directly by the user. NOTE: TopSolid uses an embedded Microsoft SQL Server to store project documents and data.