An alignment tool 1 for use in marking a surface is disclosed. The tool comprises a handle 6, two pairs of longitudinal arms 2,4 and 3,5 each rotatably mounted in the region of their longitudinal centres to a rotational mechanism provided in or on the handle. The rotational mechanism is arranged such that, in use, movement of one of the pairs in a first rotational direction results in movement of the other pair in the counter direction by substantially the same angle. Each of the arms carries at least one movable marking indicator 50, 53. A user-operable locking mechanism is on or associated with the handle, the locking mechanism being configured selectively to prevent and enable rotation of the arms.