This invention relates to a pendulum assembly within a laser levelling apparatus. In use, the assembly is rotatably mounted with the levelling device to hang under the effect of gravity such that opposed light emitting devices produce light on a horizontal plane. The assembly includes a main body rotatably mountable in the levelling apparatus and at least two light emitting devices mounted in or on light emitting mounting portions. At least one of the light emitting mounting positions is rotatably mounted to the main body and adjustable in its orientation with respect to the main body by an threaded adjustment means. Once one light emitting device is mounted, the adjustable one can be brought into a substantially co-linear position by movement of the threaded adjustment means. A further embodiment includes a further light emitter acting on a reflective surface to provide a substantially vertical light. Such a further embodiment fixes the position of the further emitter and reflective surface and provides adjustment mean on both other light emitting device mounting portions to arrange these co-linear to each other and transverse to the reflected light beam.