Truck Camera moves the camera parallel to the view plane.

Trucking a camera
For a target camera, dragging the mouse moves both the camera and its target parallel to the Camera view.
This button replaces the Pan button when a Camera viewport is active.
Procedures
To truck a camera:
- Activate a Camera viewport.
- Click
(Truck Camera).
The button highlights when it is on.
- Drag to move the camera and its target.
The camera and its target move parallel to the view plane, which is perpendicular to the camera's line of sight.
- Press Esc or right-click to turn off the button.
To truck with the middle mouse button:
- Hold down the middle mouse button and drag.
To constrain trucking to a single axis:
- Hold down the Shift key.
The truck is constrained to the first axis you move while the Shift key is down.
To accelerate trucking:
- Hold down the Ctrl key.