Deadbolts and Locks

"A deadbolt, or deadlock, is a locking mechanism distinct from a spring-bolt lock...[it] cannot be moved to the open position except by rotating the lock cylinder. The more common spring-bolt lock uses a spring to hold the bolt in place, allowing retraction by applying force to the bolt itself. A deadbolt can therefore make a door more resistant to entry without the correct key." (Wikipedia) Deadbolts make for excellent security devices for doors; they're inexpensive and installing one is relatively simple. There are two types of deadbolts: internal mount and surface mount, with the internal double cylinder deadbolt being the most secure.

How-Tos Tips and Techniques

• DIY Advice: Installing a Lockset
  Before installing check that the new dead bolt will fit in the hole and that the existing mortises for the latch and the strike are not too large.
• Ask The Builder: Deadbolt Installation Tips
  The installation of a deadbolt lock requires a certain level of skill.
• HomeTips.com: How to Fix Locksets and Doorknobs
  Many lock-set problems can be corrected before they become so serious that the lock set will not work.
• About.com: Install A Deadbolt
  Learn how to install a deadbolt on your front door, so you can have an added sense of security in your home.
• This Old House: A Lock on Style
  Home security is a lot more sophisticated these days, but even in an age of motion detectors and hidden cameras, an entry lockset is still your first line of defense against intruders.
• DoItYourself.com: 9 Tips for Selecting a Deadbolt Lock
  Home security begins at your front door, with a deadbolt lock.
• Repair Home: Replacing a Cylinder-Style Lockset
  Cylinder-style locksets are in almost every home and are the type that have no deadbolt attached and have either a handle-mounted push-button or twist lever lock on the interior knob.