We clip the zippers on our inner liners which locks them into place for the purpose of child safety. Adults can still gain access to the foam if needed by using a paperclip in place of the zipper handle.
You will notice that the zipper handle has been removed. This is a child safety precaution to prevent access to foam.
Insert a paperclip as shown to allow the zipper to move. Don't forget to remove paperclip when you are done.