Bulls eye levels are really nifty for getting the horizontal stabilizer flat. These are just round discs that have a bulls eye in the middle while looking down on it. Simply lay one or two (one on each side of the vertical stab) on the horizontal stab, get the bubble in the center of the bulls eye, and the tail is level. Use whatever you like to keep the plane secured in that position and you will have both hands free to work with the wing. Just keep the bulls eye levels on the tail to check from time to time to assure that the tail end did not move. These things are like two dollars each and your friendly home improvement store should have them.