When you create a mullion assignment you need to specify the mullions in the grid to use that assignment. There are two options for selecting mullions:
- Use Location to assign a definition to the start, middle, or end mullions of a vertical grid or the bottom, middle, or top mullions of a horizontal grid. If there is an even number of mullions (four or more), Middle refers to the two mullions in the middle of the grid. If there is an odd number of mullions (three or more), Middle refers to the one mullion in the middle of the grid.
- Use Index to assign a definition to specific mullions based on mullion numbers. Mullions are numbered from left to right or bottom to top. For example, typing 1, 2, 3 would assign the definition to the first, second, and third mullions.
- Click
. 
- Expand Architectural Objects Door/Window Assembly Styles. Note: Alternatively, select a door/window assembly in the drawing, and click .
- Select a door/window assembly style.
- Click the Design Rules tab.
- In the left pane, select a grid.
- Select an existing mullion assignment or click
to create a new one. - Select a mullion assignment:
If you selected… Then… Location click the Used In column, and click 
. Select the mullions you want to use this assignment, and click OK. Index enter the mullion numbers separated by commas in the Used In column. For vertical grids, mullions are numbered from start to end and, for horizontal grids, mullions are numbered from bottom to top. Note: Do not assign multiple definitions to the same mullion because only the last definition assigned to the mullion is used. - Click OK.
Any mullions that are not assigned a specific mullion assignment use the default mullion definition.