This is a parametric control horn for radio-controlled gliders and planes. Edit the included OpenSCAD source to change any of the parameters such as: Cut a hole in the control surface to accommodate the squarish section and glue in place with your favorite glue. The line through the centers of the holes should pass through the hinge of the control surface. The gusseted part should lie flat on the surface once the horn is affixed and helps to keep the horn at right-angles to the surface.