Doorknob locks offer no security. They can easily be forced open. Chains don't provide security either. They are only good for privacy. All doors leading into the house should have a deadbolt lock. Install single cylinder deadbolt locks on all exterior doors. Bolts should have a minimum bolt length of 1 inch. Strike plates should have screws that are at least 3 inches long. On all exterior double doors, install flush bolts at the top and bottom of the inactive door. These should be made of steel and have a minimum bolt length of 1 inch. Install deadbolt locks on all outside sliding glass patio doors. You should also use a back up locking device such as a wooden stick that is placed in the lower track to prevent the door from opening. Better security can be obtained from thumbscrew-type locks that are mounted on both the top and bottom tracks. Install good locks on all doors that lead outside through garages or storage areas. Re-key or change all locks when moving into a new home. Install good locks on gates, garages, sheds, etc. If you use a padlock, you should use one that has to be opened with a key and cannot be opened by bolt cutters or pry bars. The shackles should be made of hardened steel and be at least 9/32 inch thick. It is even better to use a "shielded" padlock that is designed to protect against bolt cutters. Combination locks should not be used because they offer very poor security. Use a multi-frequency opener on electrically-operated garage doors, and make sure that the bottom cannot be lifted up to allow a burglar to crawl under the door. Use hardened steel hinges, hasps, and padlocks on hand-lifted garage doors. Install cane bolts or sliding hasps on the inside of garage doors to provide additional security. Go to a locksmith or hardware store for advice on locks.