First remove the central threaded stud using coins or a screwdriver. The 2 elbowed connections arms can now be detached from each other.
1. Lay the ROK on a bench/table and knock out the metal pin that connects the main arm to the elbowed connection arm. (Sometimes a spray of WD40 or equivalent is needed to loosen the pins if they are too tight.)
2. With the pin removed, the connection arm is free. Take care not to discard the 2 bushes.
3. Insert the bushes into the new connection arm, place in the correct position on the main arm and reinsert the steel pin by tapping with a hammer. Ensure that the pin is sub flush by tapping it carefully in with a masonry nail.
4. Align both arms over the central hole in the plastic piston/plunger, push through the stud and retain with the threaded stud