Object locking allows you to choose various elements (images, text boxes, lines/shapes, etc.) and lock them so they cannot be moved or edited. This is especially helpful when designing busy pages where there is a lot going on.
To lock an object, simply click on the object and look for a lock icon in the left panel. Click the lock icon and that will lock the object. Notice you will no longer be able to move or resize the object. To unlock the object click the unlock icon in the same left panel.
Note: Objects can be locked/unlocked by any team member that has access to edit the page