Abstract: To meet the needs of 3D solid modeling and applications，we focus on the construction of true 3D solids to support the 3D objects in the real world，regardless of whether the representation of the 3D object is manifold or non-2-manifold. In order to construct true 3D solids，a broad definition of true 3D solids that satisfies the requirements of representations of the physical entities in the real world is presented. Then we explore the rules that a true 3D solid should comply with and present relevant validation methods. Some repair methods were developed during the process of constructing true 3D solids that fulfill the rules for those 3D objects that do not satisfy the rules or validation methods.