Transparent simulated components (4) are inserted into a test board (1) in an insertion machine for inserting such electrical components into printed-circuit boards at defined points. The simulated components are provided with scale-type markings (5). The test board has reference marks (3) with scales which are parallel with these scales and overlap said markings (4). The two vernier-type scales enable scale displacements to be read more clearly in the case of deviations from the ideal position.