Double bubble scriber. For outdoor or indoor use. Extremly robust 3D printet scriber. For added rigidity, each arm has an 8mm threaded steel bar in the centre of it’s entire length. Fully ajustable levels make calibration easy. Uses Ficher Space Pens. These pens can operate down to -30c! The pens sit in pen holders which can be rotated 360 degrees. Suitable for scribing all types of log building. Comes in a strong carrying case. A dummy pen is also provided for those who prefer scribing with only one ink cartridge. A downloadable video showing how to scribe Norwegian style notches comes with the product.