What must you click in a family to associate the geometry lines with the reference planes?

In Revit, associating geometry lines with reference planes is a critical step in establishing a relationship between elements in a family. This process is essential for ensuring that the geometry behaves correctly when the family instance is adjusted.

The padlock icon signifies the act of locking or associating lines or geometry to reference planes. When you click the padlock icon, you create a constraint that binds the geometry to the reference plane, allowing for controlled manipulation of the geometry based on the reference plane’s position. This ensures that any movement of the reference planes directly affects the associated geometry, maintaining the design intent and stability of the family object.

Using the padlock helps in managing the relationships among various elements in a Revit family, which is particularly useful when creating flexible models that may require future adjustments. Other icons, such as the wrench, chain, or link, represent different functionalities that do not specifically pertain to associating geometry with reference planes in the same manner.