Type of LatchesThe latch is a spring bolt that actually holds the door shut. This is in contrast to the deadbolt, that had NO spring, and must be manuallyengaged. There are two primary types of latches, the springlatch and the deadlatch.The springlatch is much more convenient, when the door is shut, the springlatch springs into place, locking the door shut. This is thetype of latch found on most key-in-knob type door locks. The problem with the springlatch is that it is easily defeated by sliding a plasticcard or thin knife and forcing it back. To prevent this, a latch guard can be installed. This is a device constructed from heavy steel foldedlengthwise at a ninety degree angle or a T-bar shape. It is usually anywhere from six to twelve inches in length and is fastened to theedge of the door by bolts. The latch guard hides the latchbolt, and prevents any tampering with it.The deadlatch cannot be shoved open like the unprotected springlatch can. When the door is closed, the latch bolt is secure in the lockposition and acts as a deadbolt (a bolt that is not spring loaded, and resists any end pressure). The deadlatch resembles a smaller, beveledbolt projecting from the latchbolt. On some designs, the deadlatch takes the shape of an additional bolt, somewhat smaller, and usuallyplaced higher up on the lock body. A key or interior locking mechanism must be used to engage the deadlatch and lock the door.