Getting the castle nut started on the bolt or stud, in a place without a lot of finger access  is the first major hurdle to be faced. But finally a couple of threads catch, and with a sigh of relief, I find that I can get a socket on the nut.  

Now, torque it down, stopping a little shy of final tightness, knowing that I will have to torque just a little more to get the slots on the castle nut to line up with the hole in the bolt.

This is going smoothly, and I should be done in time for lunch.

Just before starting the nut on, I remembered to notice the orientation of the cotter-pin hole in the bolt. Not surprisingly, since I am very experienced at this sort of thing. So  leave the nut with slots lined up where I remember the hole being.

With two fingers or needle-nose pliers   reach down with the cotter pin and start jabbing it into one side of the slot.  It just won’t go in.

 No problem, just take the socket and turn the nut a little one way or the other. No luck, one way or the other.

 Wait a minute. Didn’t the head of the bolt turn some when I was tightening the nut.?  That would change which direction the hole points. Or did I pick up an “A” bolt without a hole.

OK, take the nut off and start all over. This time don’t let the bolt turn.

Results are about the same. Maybe I can get a small mirror down there and see if I can spot the hole through the slot.  That doesn’t work. Maybe I can shine a flashlight on one side, and enough light will come through the hole to make it easier to find.Well!  you get the idea!!

Here is a tip that makes this whole process a lot easier and quicker. On the end of the bolt or stud, take a marker pen and draw a line across the end that lines up exactly with the hole for the cotter pin or safety wire.

Now start the castle nut on, and torque it down.

Line slots on the castle nut up with the guide mark that you made on the end of the bolt. Now the pin or safety wire will slip right through.

Go to lunch early!!