Low Ceiling Clearance - #8146 Drop Plate For use where low ceiling clearance prevents normal top jamb mounting. This plate is used when clearance is from 1-7/8 to 2-7/8 (48mm to 73mm). Where ceiling clearance is less than 1- 7/8 (48mm) see #8148 Drop Plate detailed in the following text. Overhead Door Holder - #8146 Drop Plate For use where a surface or concealed overhead door holder prevents normal top jamb mounting. This plate drops the closer and allows arm mounting screws to clear the bottom of the door holder. This places the centerline of the arm mounting screws at 2-7/8 (73mm) from the top of the door. Stocked Product 689 ( aluminum) 690 (dark bronze) Low Ceiling Clearance - #8148 Drop Plate For use where the ceiling clearance is between 1- 1/2 and 1- 3/4 (38mm and 44mm). Stocked Product 689 ( aluminum) 690 (dark bronze