How to lock model in dynamics 365?

you can lock model in dynamics 365 to disable customization on this model.

just go to dynamics 365 in visual studio and click model management to update model parameters 

select your model and click the locked checkbox 

click next 

click finish

To validate this option, 

just create a new project and right click then click properties 

and set model for the locked model as the below 

try to add a new item to this project 

and select any item like security role or table..etc

thanks.