A pattern file is a text file that contains definitions for model or drafting patterns in a project.
The file must be saved with a PAT extension.
In a typical installation, a number of sample PAT files are installed and can be used to create custom fill patterns. The sample PAT files can be found here:
%ProgramFiles%\Autodesk\Revit LT 2015\Data
%ProgramFiles%\Autodesk\Revit LT 2015\ACADInterop
If you create a custom pattern file for Revit LT, it can be stored in any location. After Revit LT imports information from the pattern file, the actual file is not referenced. If your organization develops a PAT file containing standard patterns to use in projects, you may want to store the file in a network location for easy access by all Revit LT users.
For information on using a custom pattern file, follow the procedure in Creating a Custom Fill Pattern.