The plastic pieces you are talking about go over the control horns after you have inserted them thru the control surface. look at them carfuly they have a pointed edge on them that catches the teeth on the horn. make sure the pointed edge is down. you will have to use a hoby knife or razor blade to lightly open the hole for the control horn to go thru. they go in from under the elevator and looking from the back of the plane from the right of the stablizer. Hint to you, the first thing I did when i opened the box was throw away all the screws and use standard survo mounting screws for all but the tail fin. you will have to use the 2 stianles screws as they are just the right size to go thru the holes.