Auto rotation problem.

[Shilo]

WHY CANT I LOCK THE SCREEN IN VERTICAL MODE?

[Uliwooly]

You don't have to scream, you can not do so, you will need a different lock screen app from the play store 

[dquilon]

You can get Screen Rotate from Small Apps in the Play Store... it installs a small app that can be found in the Task Manager / Recent App list and you can access it anytime...

Highly recommended