How Safe is the Lock on Your Door? You had better investigate at once because Roy Post, famous criminologist and author of many articles on crime detection, reveals that almost any lock can be opened with just his fingers and in exactly nine seconds. In this series of pictures, Post shows how this trick is accomplished and what you can do to prevent it. Post is examining the cylinder from an ordinary door lock, the same kind you probably have on your door. Notice the small v indentation to which he is pointing. It is just 1/8 of an inch deep and that is all the protection you have. You door may be six inches thick, your lock may be a new and expensive one, but there is only 1/8 inch between the burglar and you property. Watch carefully.