The August Smart Lock retrofits to your existing Single-Cylinder deadbolt, allowing you to send a virtual key to anyone you choose to have access to your home. Your guests then use their smartphone to gain access to your residence without the need to exchange physical keys. You can specify the duration that the August keys are active for before expiring, or disable them at any time. An August system consists of a small, easy-to-install smart lock device and a mobile app. With August you can still use your physical keys and manually unlock or lock your door from the inside.