Key Gauge from Factory Brands helps you determine the key number from Schlage and Kwikset keys. Using the iPhone's high-resolution Retina Display, Key Gauge will shown you actual size images of popular keys. You can dial in the key bitting and the image on your iPhone screen will change to match that of your key. The image shown can also be flipped over to show the back of the key by just touching the title bar.
After the image on the screen matches that of your key, you can record the key number, any stamping notation that it may have and any notes. The table of key numbers, key stamps and notes can be emailed out of the application as a CSV file at any time.
View App in iTunes App Store: Key Gauge | 
