You can view and modify the common properties of multiple entities in the Properties window.
If the value of a certain item is not identical for all the selected entities, the cell appears blank in the Properties window.
If you modify the blank cell, Tekla Structural Designer applies the new setting to all the selected entities.
If you have selected multiple entities of different types, the property information is displayed separately for each type. Use the list at the top of the Properties window for moving between types.