One of the most common operations in ship building is the alignment of a tool with respect to a mock-up. If the tool is mounted onto a robot manipulator then the problem is to properly control the latter such that the desired alignment is accurately achieved. Among various sensors to be used in conjunction with robot control, vision has a number of advantages: it is low-cost, fast, covers a wide field of view and can operate in various configurations such as cameras mounted onto the robot itself or cameras mounted onto independent fixtures. We briefly review the main components of a visually-guided robot system, we compare the relative merits of hand-held cameras and independent-held cameras and we illustrate the alignment of a welding torque with respect to a mock-up. The work is done cooperatively between INRIA Rhône-Alpes, The University of Cambridge and Odense Steel Shipyard as part of the ESPRIT-IV Reactive LTR project 26247 VIGOR (Visually guided robots using uncalibrated cameras).