Document created by Pencil, an open source GUI prototyping tool; saves a page with different design elements for a targeted user interface; used for making software mockups for mobile (iOS, Android, etc.), Web, and desktop platforms.
Pencil documents can contain common shapes, basic Web elements, desktop widgets, flowchart objects, and various other design elements.
Pencil can export documents to .PNG, .PDF, .SVG, .ODT, and Web formats. This is helpful when sending design documents to clients and developers, as well as for including the design in presentations and other documentation.