Lock Object

Next to each Object (Text, Images, Shapes, etc) in the Object List is a lock icon.

Clicking on the lock with lock or unlock the object.

When locked, an object can not be moved and its settings can't be changed. This is helpful when you have an object that you will be placing other objects on top of. When locked you can easily move the other objects on top of the locked object without worrying about accidentally moving/changing the background object.