To modify the clearance height, location, and skew

Review and modify the clearance envelope height, location, and skew, and update the bridge's vertical profile.

1. Select the bridge to display its attributes in the Stack
2. Expand the Clearance panel and toggle Show envelope to the on position.

![Show Clearance Envelope](../../images/ill_toggle_show_envelope.png)

Note: The clearance envelope is shown on your model as a purple box.

3. Click the Height field to input a new value.

Note: The height of the clearance envelope is based upon road elevation, not terrain elevation.

4. To modify the location and skew of the clearance, click the value(s) next to Start Offset and/or End Offset, Base Elevation, or Skew. Input any desired value(s) then press Enter.
5. Right-click on the bridge and click Update Vertical Profile to enforce the new clearance attributes.

![Update Vertical Profile](../../images/ill_show_clearance_envelope.png)

Your bridge will re-generate with your modifications to the clearance envelope attributes.