Bolt throw is the distance a deadbolt slides out past the edge of the door when you lock it. That extended section crosses into the frame and keeps the door from swinging open. Throw matters only if the bolt enters the strike opening cleanly and seats into solid material behind it. A long throw into a misaligned strike or a weak frame holds poorly.
What bolt throw means
On a deadbolt, the bolt is the solid metal bar that slides out when you turn the key or thumb turn. Bolt throw is how much of that bar travels past the edge of the door once it is fully extended. Lock descriptions mention it because the throw is the working part. Whatever stays inside the door does nothing to hold it shut.
Throw is one factor, not a score. The figure on a lock description describes the lock alone. What your door gets depends on where that bolt lands.
How the bolt, strike, and frame share the load
Picture the door closed. There is a small gap between the door edge and the frame. When you lock, the bolt crosses that gap, passes through the strike plate (the metal plate on the frame with a hole for the bolt), and enters a pocket cut into the frame behind it.
How much bolt is really holding depends on that path. A wider gap uses up some of the throw before the bolt reaches the frame. A strike opening sitting slightly high, low, or to one side makes the bolt rub or only partly enter. And the pocket behind the strike has to be deep enough for the bolt to extend all the way.
When someone pushes or pries at a locked door, the force runs through the bolt into the strike and then into the frame. The bolt is usually not the weak link. The strike screws, the wood around the pocket, or a frame that flexes away from the door tend to give first.
Does a longer bolt throw make a door more secure?
A longer bolt throw does not make a door more secure by itself. More throw puts more bolt into the frame, which helps when everything around it is sound. In a loose, cracked, or worn frame, the extra bolt just has more weak material to lean on. A strike that is out of line can also stop a long bolt from extending fully, so the throw printed on the package never happens on your door.
Throw versus bolt length
Bolt length is the size of the whole bar, including the part that stays inside the lock body. Bolt throw is only the part that comes out past the door edge. Two bolts of similar length can throw different amounts depending on how the lock is built.
Neither figure tells you what the bolt is made of, how sturdy the lock body is, or what shape the door and frame are in. Those are separate questions, and a lock sold as stronger is worth judging with the frame in view.
What you can check on your own door
Watching the deadbolt work tells you a lot, and none of it requires taking anything apart.
- With the door open, turn the deadbolt. The bolt should slide out to its full stop and back without catching.
- Close the door and lock it slowly. If the turn gets stiff partway, the bolt is dragging on the edge of the strike opening.
- If you have to lift, push, or pull the door to get the bolt to extend, the door and strike have drifted out of line. Sagging hinges, a swollen door, or a shifted frame are common causes.
- Once locked, push gently on the door. A slight rattle means the bolt has room to move in the strike. A door that shifts noticeably suggests the bolt is barely engaged or the frame is giving.
- Look at the strike plate. Scrape marks on one side show where the bolt has been hitting.
Those signs sort the problem. If the bolt runs smoothly with the door open but drags when it is closed, the lock is probably fine and the issue sits in the strike, door, or frame. If the bolt is rough or stops short even with the door open, the lock itself needs attention.
Don't force a bolt that binds or crank the key harder. That wears the lock and can bend the bolt or crack the jamb.
If the bolt drags, falls short, or the door rattles once locked, call Bklyn Locksmith at (347) 500-8711. You can also bring the question to the walk-in shop in Greenpoint or ask for a mobile visit, any day from 9 AM to 11 PM.
Frequently asked questions
Can a deadbolt be misaligned with the strike plate even if it turns smoothly?
Yes. A deadbolt can turn smoothly and still sit off-center in the strike plate. If the strike opening has been widened over time, a bolt that lands high or low passes through without dragging, so the turn feels fine while the bolt has room to shift. Look for a strike opening noticeably larger than the bolt, or bright wear along one side of it.
Does a deadbolt on a metal door work the same way as on a wood door?
A deadbolt works the same way on a metal door as on a wood one: the bolt crosses the gap and enters a strike in the frame. What changes is the frame around the strike. A wood jamb holds the bolt in a bored pocket, so the condition of the wood matters. A metal frame is often hollow, so the strike and anything behind it carry more of the load.
Is a deadbolt that only partly extends still locked?
A deadbolt that only partly extends is not doing its full job. Many deadbolts lock the bolt in place only at full extension, so a partly thrown bolt can be easier to push back and has less of itself inside the frame. The usual cause is a strike pocket that is too shallow or out of line, or a door that has shifted.
Will replacing the lock fix a deadbolt that meets the frame badly?
Replacing the lock usually does not fix a deadbolt that meets the frame badly if the bolt works fine with the door open. In that case the cause sits in the strike position, a pocket that is too shallow, or a door that has dropped or swollen, and a new lock goes into the same opening. A lock that is rough or stops short with the door open is a separate problem.