Jam nuts on the shank of a rod end do two things.
One, they keep the pushrod from unscrewing off the rod end threads.
Two, they lock the threads in place with a positive load....with slack between male and female threads they would wear.
You're building an -8, so be aware of a detail. Take particular care in locking the jam nuts on the pushrod between the rear control stick and the elevator bellcrank. If the two rod ends are not is exact alignment you'll find that rod end position will limit aileron travel. Well, actually it won't; given enough force it will unscrew one of the jam nuts.
