When adding or modifying a curtain grid, use options of the Modify | Place Curtain Grid tab
Placement panel to control the placement of grid segments on a curtain wall panel.
Video: Place Curtain Grids- All Segments: places grid segments on all panels where the preview appears.
- One Segment: places one grid segment on one panel where the preview appears.
- All Except Picked: places a grid segment on all panels except those you select to exclude.