The locomotives in this part of the country run short hoods forward, and that is were the F located, at that end of the engine, towards the bottom of the side sill. There is mainline operation, yard operation. Mainline is a lot more restrictive on making movements, than yard movements. After all, the mainline is for 6500 ft loaded freight trains to get from point A to point B, in the least amount of time, non stop. To Move Freight! So on the mainline, these trains most generally have a directional warrant, that is, permission to travel in one direction (forward,) only. That warrant does not give them permission to back up, or more appropriately, make a reverse movement. IF, they have to make an unscheduled reverse movement, say to set out a bad order car, they have to get permission from the dispatcher. If they get permission, and they start the reverse move, (pushing the car,) they're doing a "shoving" motion. Now, the "point", (the end of the car that's leading, into the side track,) must be protected, (somebody must watch the leading end of the car the entire movement start to finish, so that something doesn't happen.) Radios and hand signals are used in setting out the car. No horn is sounded when the engine goes to move, not needed. (But there are special circumstances.) A lot of rules/processes for movement on the mainline. IT IS VERY DANGEROUS!
The "local", serving industries along the mainline has different rules/procedures for reverse movement.... as does the switch crew in yard limits moving cars around......