Disclosed is a method of producing an assembly tool for assembling a first system comprising one or more components. The method comprises: for each component, determining, when the first system is attached to a second system, a position and orientation of that component relative to the second system and positions and orientations relative to the second system at which that component is to be supported; providing a frame; attaching, to the frame, a reference structure; providing a plurality of pickup devices each having a receiving element for receiving a component; and securing each pickup device to the frame such that a position and orientation relative to the reference structure of each receiving element is the same as a position and orientation at which a component is to be supported.