Similar to Building Regulation Drawings, Tender Drawings are a also set of documents that go into more detail to combine studying the nature of a project including client requirements.
All these come together to assist with the construction process, considering details such as insulation, finishes and usually every material and method used for the construction.
The more clear and comprehensive the details provided are, the more difficult it becomes for the contractor to get away with unjustified extras in the construction process.