I worked as a railroad brakeman from 1979 to 1984. I was there long enough that my seniority level was in the middle of the pack about halfway through my tenure. I could hold down some jobs without getting bumped by higher-seniority guys, at least for a while, but some popular jobs I could never bid on and win, because they would usually be won by somebody with higher seniority.
One time, for a period of a number of months, I was able to hold down a pool crew job, however, I was the youngest seniority-wise of the two brakemen on the job. Seniority convention was that the senior brakeman got to choose whether he wanted to work the head end (locomotive) or the rear end (caboose), so I usually worked the locomotive. However, if the senior brakeman was on personal, sick, or vacation leave, the junior brakeman could pick which end he would work, regardless of the seniority of the extra brakeman sent to protect the senior brakeman's job.
One day, my crew was deadheaded by van to a midpoint station to run a train back to our home terminal. We had an extra brakeman (off the extra board) senior to me, so that meant I got to choose which end to work. Normally, a brakeman would choose the rear end because that was safer and easier work. As we were waiting around on the station platform to make the exchange with the crew that was bringing the train into town, I could tell by the talk between the extra brakeman and the conductor, that the extra brakeman thought he would be working the caboose. He was senior to me, and I had already been working for several years, so how he didn't know this seniority rule is hard to explain.
I probably should have brought it up with him on the spot, and stated that I was going to work the caboose, but I didn't. Here's what I did instead: The train was being brought up to the station by the inbound crew, and we were going to do a running exchange, i.e., the train would not stop, only slow down enough where everybody could get safely off and on. I saw where the extra brakeman had stationed himself to board the caboose, so I stationed myself about 50 feet down the platform closer to the direction the train was coming from. When the locomotive came by me, I let it go by, and did not get on. I turned my head towards the extra brakeman, and I could see that he was totally confused by my not boarding the locomotive. I added one more ingredient: Just before the locomotive steps got even with him, I said, "You'd better get on." He got on the locomotive, and I ended up boarding the caboose as was my right.
When we got to our home terminal about five hours later and were boarding the van to go to the yard, I overheard the extra brakeman asking the conductor about what I had done, and the conductor backed me up by stating that that was the way seniority worked on freight trains between a job's regular brakeman and an extra brakeman. The extra brakeman was a nice guy, and didn't raise a fuss, but I still wonder how he went through at least three years of work and never came across a situation where that seniority convention came into play.