© 2018 Journal of Ship Production and Design. All rights reserved. As a result of increased pressure to reduce cost and delivery times of modern ships and submarines, many shipyards are revising their processes and toolsets to optimize the management of sister ships. This article describes how a strong CAD–PLM integration with efficient functionality on the CAD side ensures better design and production in a multivessel context. To address this complex challenge, and after several years of experience in the development of the FORAN CAD/CAM system that is used in many important naval programs, SENER identified some remarkable assumptions to be considered: 1) In a sister ships environment, each vessel or unit will have a CAD project, 2) There will exist a class project to centralize the CAD locking and applicability data, 3) The existence of an item in the CAD project is considered as an item occurrence in that project, 4) Modifications on an item will be done from a single project, but all other projects sharing the item with the same applicability will also be locked to prevent modification on them by other users, 5) Once the modification changes are applied, the CAD will update them in all projects sharing the items applicability (multisave concept), 6) The use of applicability on an item within a sister ship series might be to all vessels (e.g., 1-UP), to all vessels newer than a specific one (e.g., 3-UP), to some vessels specifically (e.g., 1-UP), or to a combination of the above (e.g., 1-UP), and if no applicability is set, it means “effective for all vessels” (1-UP), and 7) The FORAN system already had functionality related to sister ships management in the past, but it has been notably improved with the complete FORAN–PLM integration. This article presents in detail the architecture of the applicability solution and the expected advantages and benefits for commercial and naval shipyards.