Kabiru

A kabiru - the plumb bob every mason in Kenya works with. It is the simplest instrument on any site and one of the few that cannot be wrong: a pointed metal weight hung on a line, left to settle, and read against the work. Gravity does the measuring, so unlike a spirit level it needs no calibration, cannot drift out of true, and does not care whether the ground it is standing on is level. Used for checking a wall is rising plumb as the courses go up, setting out and truing door and window frames, plumbing columns, posts and gate pillars, dropping a line down a shaft or void, and transferring a point from one floor to the one below. Let it stop swinging before you read it, and shelter it from wind, which will lie to you.