The flex power tools alc 21 basic self levelling laser has one horizontal and two vertical laser lines at a 90 angle it is operated with a simple on button operation and there is a lock for safe transportation it has exceptionally bright laser lines that are still highly visible even in poor lighting conditions the laser has an optical warning signal when self levelling range is exceeded and the self levelling can be switched off the laser is ideal for aligning framework and there is a 14in trip