There is also a chance that someone tried to tamper with your lock and instead of opening it got stuck.
Lockwood sliding door lock jammed.
There are various mechanical reasons for this which includes a stuck pin worn out tumbler etc.
Lockwood 8653 sliding security screen door lock.
Coat your door key with powdered graphite or spray.
Tip if the door locks perfectly while in the open position it is an adjustment issue.
How to get your cusfd stuck lock un stuck.
However if it is still hard to lock while in the open position it will more than likely be a mechanical fault probably needing replacement parts.
With a well established reputation for high quality products this iconic brand provides a wide range of locking solutions to residential housing commercial building and industrial application markets supported by an extensive distribution and after sales support network.
Lockwood is the leading brand in the australian locking industry.
These are the main culprit in 90 of the cases.
If you exhaust the list of quick fixes and repairs to no avail you ll have to call a locksmith or replace a permanently jammed door lock.