How do lock the I-pad to keep it in the horizontal position?

Toggle ON screen rotation lock by swiping a finger downward from the upper right corner of the iPad’s screen to reveal the iOS/iPadOS Control Centre.

Look for the button/icon with a padlock symbol inside of a circular arrow.

Tap that icon/button to lock the screen rotation.

Good Luck!

Italy1952 Said:

"How do lock the I-pad to keep it in the horizontal position?: how do I lock my i-pad to keep the screen in the horizontal position. this is my third submitting this question."

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Go Here: Change or lock the screen orientation on iPad - Apple Support

I have searched and I can find no other posts from you, using that username. As you haven't stated what version of iPadOS/iOS your iPad is running, I am basing my reply on mine, which is running iPadOS 15.1. Pull down from the top right corner to reveal the control panel, and then select the rotation lock button.