Smart Ruler Pro is the 1st set of Smart Tools collection (ruler, protractors, level, thread). It integrated 6 simple and useful tools into this app. Here is the list. 1. Ruler - for length. 2. ProtractorⅠ(Touch) - for angle. 3. ProtractorⅡ(Plumb) - for slope. 4. ProtractorⅢ(Camera) - goniometer, clinometer. 5. Surface level - for level.