Extra-rigid rectangular aluminum profile with patented anti-knock protection for direct correction of deviations, building material is aligned with the anti-knock protection with light taps, no need to change tools, handle openings for optimal and comfortable handling, reinforcement ribs for high stability and a secure grip when working, spirit level with an exact Plane-milled measuring surface, no discoloration on surfaces, e.g. on exposed masonry, always at eye level, the second vertical spirit level, which is offset to the middle, enables easy reading in all measuring positions, shock-absorbing, removable end caps, the two-component material mix protects the profile from impacts, simply close clean thanks to the electrostatic powder coating, STABILA built-in technology ensures long-term precision, measuring accuracy in normal and reverse position ± 0.5 mm, particularly suitable for bricklaying work, for example when setting a wall