Have you asked IT if this is indeed an "unsupported configuration"?

No, that's a good idea. What could I do professionally if htey said it's fine with them?

"How can I convince my manager to let me work this way permanently?" - apparently you can't since your manager doesn't have much of a clue. Perhaps your IT group can convince him for you.

@MichaelKohne that's an answer!

if your boss makes you work slower on purpose, i don't have a lot of faith in the whole operation, do you?

Might be an opportunity to start gunning for the manager's job.

@SethR - "'If I let you do it then I'll have to let everyone do it' - I fail to see the problem with that." I see the problem with that. Hint: It's not the monitor.

@WesleyLong, oh there's definitely a problem here, but it isn't with letting everyone position their monitor is whatever way makes them most efficient.

@MichaelKohne asking your boss for permission to ask IT for permission? If a manager reacts negatively to asking IT for permission to do something that IT has rules about, then it would be good to get away from that manager A.S.A.P. Monitor issue aside, there will be countless other issues.

Managers are there to help employees succeed. When a manager inhibits an employee from succeeding in order to make themselves look better, only awful outcomes can occur for everyone.

I suggest to choose your battles carefully. This isn't really a hill you want to die on

@BradThomas this may not be, but if the boss is going to balk at this even when he knows the cost is decreased productivity and morale, then this is the first of many, many hills. This is simply an attempt to codify the pecking order, via being, well, a pecker.

Stop doing it anyway. That only undermines your position and makes you insubordinate.

@BradThomas, yes, you have to pick your battles but you also have to set boundaries.

Once IT says it is ok, send the manager an e-mail (cc'ing the IT person) reiterating the conversation and that it is ok. This lets him know the rule and makes a paper trail if he wants to try making trouble in the future.

Are you otherwise comfortable with this manager and are they sane? I would look for a new position if not.

Place a request with IT to use the monitor in that configuration. Be sure to exercise whatever appropriate channels are required by your company's policy.

@CramerTV I agree it's sometimes necessary to set boundaries, but then you should do that only when you are actually setting a legitimate and reasonable boundary. Sure we can all agree it appears that the manager is being a bit of an idiot here, but that is his privilege in this situation. OP has no right whatsoever to dictate the orientation of his monitor, as far as I can see. He might have an overwhelmingly reasonable case to make, but no right to insist. Having a reasonable case doesn't necessarily equate to being able to reasonably set a boundary.

My office offers a "fit" check from a qualified person. Consider that you might find it easier and less painful to tilt your head up and down rather than all the way left and right, because two monitors in vertical position are narrower.

@Brandon - asking a control freak manager for permission to ask IT lets the control freak feel in control. This gives into the manager's need to establish pecking order, while still potentially making headway. Basically: work within the boss's oddities to get what you want.

every time it only lasts about an hour before he comes over and tells me to put it back You won't convince someone that obsessive, IMO. This is about your manager's ego, about exercising power and control, not about anything practical because it has no practical impact on your manager at all but they are prepared to invest time in forcing you to conform to what they want.

I must know how this battle of the monitor orientation turns out.

@BradThomas, I wasn't suggesting that the OP insist anything to the manager. The manager invoked a "non-standard" configuration. The OP should verify what that means, whether it be for workplace ergonomic policy or IT requirements. Once it is established that the manager doesn't have a legitimate claim, the OP needs to stay within company policy - not a manager's preferences, imho. My manager wouldn't buy a 4k monitor to develop a 4k sized application - so I bought a 40" 4K TV. I justified the expense by noting that I sit in front of it 8 to 10 hours a day. It should be what I want.

When he said "If I let you do it then I'll have to let everyone do it", your reaction should have been: "so?" What's the problem with having employees orient the monitor in the way that's most comfortable and productive? Does he mandate a chair height rule for uniformity even if it's not a comfortable/ergonomic height for everyone?

@Johnny Obviously there is not possible way for the IT department to overcome that obstacle. The company would last 20 minutes tops until the amount of computers on fire would be too much to keep the building occupied without risking everyone's lives.

@WesleyLong you got any more of those hints for us denser folk?