Agency has 3 core menu styles for the Main Menu: Suckerfish, DualFish, and Dropline.
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To set up the menu simply open your module manager and create a new main menu module and position it in the menubar position, turn the title off, select main menu, select list style and make sure the Always show sub-menu Items is set to YES.

Next, open the advanced parameters and in the Menu Class Suffix and Module Class Suffix add your menu style: suckerfish, dualfish, or dropline (MAKE SURE TO PUT A SPACE BEFORE)