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Welcome to the first post in a series about common locksmith problems. Today, we’re discussing the so-called snib drop.

The snib button is the little button on the inside of most Yale locks, which allows you to hold open the latch, or to prevent the key from turning in the lock by fixing the bolt in place, like a deadbolt (in the Yale lock, right, the circle in the centre of the lock is the snib button).Nightlatch

The first feature is very practical for when you’re running in and out of your front door a lot, e.g. when you’re moving furniture in and out. The second feature has a much more niche application.

While the deadlocking aspect of the snib button is kind of practical, it has a big drawback: it prevents people who have a key from getting in. So if your spouse will be home late, and you apply the snib and then go to bed before they return, you’ve locked your partner out.

The snib button was primarily useful during the days when most people didn’t have a deadlock. Thankfully, in the nineties and noughties, insurance companies started to force people to fit deadlocks to their doors.

…that’s great and all, but what’s a snib drop?

In theory, you can only apply the snib button from the inside of the door. This means that, even if it locks people out who have a key for the door, there should be somebody inside who can let you in.

But the snib drop is a common scenario where this is not the case.

It normally happens on old locks and doors. The door has warped over the years, making the gap between the frame and the lock relatively large. As you’re leaving the house, you pull down the handle to open the door. By mistake or through general heavy-handedness, you knock down the snib button and activate the deadlock. Normally, you wouldn’t be able to shut the door with the latch in its rigid state, but because of the warped door, you can slam the door shut.

And bang, you’re locked out. Except you don’t know it yet. You only know it once you come back home.

Yale PBS1 auto-deadlocking nightlatchSadly, there’s not much to be done to fix it. If there’s a letterbox on the door, we might be able to reach in with a tailor-made grab-arm and disengage the button, but it’s not always possible. Oftentimes it’s necessary to destroy the lock and barrel to let you into your home.

The best defence is prevention. By installing a more modern Yale lock, like the PBS1 shown right, you will avoid the issue entirely. The snib button can only hold the lock open on the PBS1, but it doesn’t prevent the key from turning when the door is shut.

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