We get the question a lot as a lock and safe company. does a double cylinder deadbolt give me more security? well there are a few things to consider before I answer this question. A single cylinder deadbolt is a lock that has a keyhole on the outside and a thumbturn on the inside. A double cylinder deadbolt has a keyhole on the inside and outside of the door. There is no other difference between the two types of locks. The difference is going to be what type of door you put these on, that is what is going to determine rather or not the double cylinder deadbolt will be more secure. Very simply, if you have a door that has glass in it or around it I recommend calling a locksmith right away and having them install double cylinder deadbolts on those doors. If the doors do not have glass in or around them than a single cylinder deadbolt will be just fine. The double cylinder keeps a burglar from breaking the galss and unlocking the door!!!