How to get this ruby in Doom: The Dark Ages (Chapter 5: The Holy City of Aratum)

https://youtu.be/QTgJms64ljw

You have to put something on this

so it doesn’t lock down. If you stand on this plate, door will open.

So, you have to put something on the plate. So look above you’ll see this, throw your shield at it.

Congrats, you got the ruby.