Door Knob Cover 2pk  Item # L111  $5.90
Door knob covers are the easiest way to keep toddlers from entering or leaving rooms.  Once installed, the cover freewheels over the actual door knob.  The side-grips on the cover must be pressed in to be able to turn the door knob and enter the room.  This cover also has a lock-guard which covers the door lock preventing against accidental lock outs.
The simple solution!