Pencil was an add on for Firefox to build wireframe / and quick prototype. To find an alternative you can check this comparison: https://socialcompare.com/en/comparison/mockup-wireframing-design-tools
Pencil was an add on for Firefox to build wireframe / and quick prototype. To find an alternative you can check this comparison: https://socialcompare.com/en/comparison/mockup-wireframing-design-tools