Smart Ideas: Revisited Business Products & Services by aebi - October 10, 20210 The Advantages of Double Deflection Grille Units Description. Design DD dual deflection grille includes two sets of separately flexible revolving blades located above the reduced jaw. The top blades can be either upright or horizontal. Grille appropriates for straight supply or draw applications and can likewise be utilized as top-mounted cord run head unit. Installation….