It can be used for an angle of 30°, but not directly or easily because the two sides with strong edges start at 45° and can increase. You can use it indirectly for smaller angles (or subtract, i.e. get 30° by measuring 90° and subtract 60°) or directly with an inside edge (less accessible). So it works, but using it between 0° and 45° is more impractical than I'd like. On the other hand, it's very well made, accurate and secure, with easy-to-read corners and three levels of high-end quality. My