Calslock Portable Door & Travel Lock ADDED PROTECTION  Provides an additional layer of security, and peace of mind from unwanted entry SMALL AND PORTABLE  This lock takes up less room than two pens and is easily added to any door USE ON DOORS WITHOUT A LOCK - resists forced entry, even if the door does not have a lock! SIMPLE - The Portable Door Lock is compatible WITH your door's existing locks PLEASE READ - The Portable Door Lock works only on doors that swing inward toward the living space