For almost a century, box lock makers have been installing intercepting safetey sears on their better grade box locks.

An intercepting seafety sear, also know simply as safetly sears or secondary sears, prevent the hammer from falling and striking the firing pins unless tha appropriate trigger has been pulled.

Most sidelock shotguns and rifles have intercepting safety sears.

You can determine if a box lock has them by looking to see if there is a screw toward the bottom of the fence or ball of the action.

See phots at Hollowell's web site: http://www.hallowellco.com/abbrevia.htm

JPK