QuiQue's Aircraft Yak-54S Assembly Manual page 23

Step 6
Install the heavy duty Dubro control
horn. Measuring from the hinge line
to the ball link's bolt should be 1 ¼"
inches. Adjust the provided titanium
rod (the longest) to the right length in
order to set the elevator at neutral
position.
The ball links are mounted on the
outside of the servo arms and on the
inside of the elevator control horns.
The titanium control rods have
reverse threads for easy adjustment.
The plastic ball link connectors do
not have any threads so when you
turn the titanium connecting rods in
place you are in essence making the
threads as you make your
connections.
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