Enterprise Architecture (EA) requires modeling enterprises across multiple levels (from markets down to IT systems). Providing tool support for such models is a challenge (e.g. model containment hierarchy, navigation difficulties, problems to relate elements between different diagrams). In this paper, we identify the requirements that a CAD tool needs to satisfy to manage such hierarchical models. We then propose a solution to meet these requirements: SeamCAD - a tool designed to manage hierarchical models. We present the key features of SeamCAD and an overview of the modeling language it uses. The benefit of the proposed solution is tool support for managing enterprise models.