Use this procedure to change the opening endcap style assigned to windows. 
Note: Each opening endcap style is generally created for use with a specific wall style. Changing the opening endcap style used for individual windows may cause the wall to display a defect marker. 
- Select the windows whose endcaps you want to change, and double-click one of them. 
 
- On the Properties palette, expand Basic, and expand Location. 
 
- Select the Opening Endcap style drop-down. 
 
- Select By Wall Style or Standard. 
Note: When inserting a corner window, if the wall corner have different endcap styles, a dialog box is displayed to inform the user about the error.