Abstract: A shimming device for installation and level adjustment of a frame in an opening of a wall structure is described. The device comprises a housing securable in a space defined between the opening of the wall structure and an outer surface of the frame. A leaf spring is secured in the housing and a bolt fastener causes the spring to extend out of the housing and retract therein. The spring, when in its extended condition from the housing, engages a surface adjacent the space. The frame is held in securement and is level-adjusted in the opening by opposed shimming devices secured in opposed spaces defined between the opening and the frame. It is pointed out that no screws are inserted through the frame for its securement in the opening. The device may also be comprised of a leaf spring which is actuable by a strapping element which is securable to the surrounding structure.