Spring latch door knobs are the least expensive and easiest to install. They operate by locking the door knob to the door and preventing a spring-loaded latch to retract. Door knobs are weak in several different ways. Things other than the properly fitted key can release the latch allowing burglars to enter. We’ve even gotten into these by putting a pair of pliers on the end and turning. The latches, when improperly installed, can be opened with a credit card. Of course a latch guard helps thwart this type of entry. We recommend on all of our lock installations that we use longer screws possibly 2 to 3 inches to attach the lock plate to the doorframe.