The Structural sub-package forms the core of BuildAMol's structural manipulation capabilities. It encompasses functionalities related to atom-level manipulations, including algorithms used to compute atomic placements during fragment assembly. This sub-package provides a rich set of functions and data classes for internal use, such as fundamental mathematical operations on vectors and matrices, explicit computations on molecular structures, and inference tasks like adding missing hydrogen atoms. The Structural sub-package serves as a foundation for most other BuildAMol functionalities. Many of its functionalities are also directly accessible through methods of the Molecule class. Therefore, in most use cases, users will not need to interact directly with the Structural sub-package itself.