There is a requirement for some leverage in just operating the locking mechanism to release the door from its closed and locked position. There are also some doors that require the leverage to lift the door a small amount so that the full weight is on the hinge for opening.

There is an option for a key lock in the external door handles to secure the plane while unattended. These would be a lock similar to one on a lockable storage box and is only designed to lock the outer handle in a closed position from the outside.