The owner came home, but his usual key suddenly no longer fits the lock.

The client's name and certain details have been changed.

Let's call the client Alexander. He used the same key for several years. One day I returned home, inserted the key, and discovered that it no longer worked.

The key looked fine. He was right from this door. But it felt as if there was another lock inside.

“Yesterday I calmly opened the apartment with this key. Today it doesn't work at all. What could have happened?

Here you first need to calmly determine the cause.

Possible explanations

The reasons may be either technical or related to changes in the lock itself. For example:

• the cylinder has failed;
• jamming occurred inside;
• the key is very worn;
• mechanism is damaged;
• the cylinder was replaced by another person with legal access;
• an error occurred with the keys.

You should not automatically conclude that someone changed the lock on purpose.

What to check first

If there is a second original key, try it. Also note:

• the key enters completely or not;
• it does not turn at all or only partially;
• has the appearance of the cylinder changed;
• is the fittings different?
• are there any signs of recent work on the door.

What if the cylinder really looks different?

If there are other owners, tenants or managers of the property, it is worth first finding out whether work has been carried out. In multifamily or rental housing, replacement may sometimes involve agreed upon repairs.

If the change occurred without the knowledge of the owner and there is reason to suspect illegal interference, this may no longer be just a technical issue.

Should I try to open the door by force?

No. If the correct key suddenly stops working, a strong impact may:

• break the key;
• damage the cylinder;
• complicate diagnosis.

It is better to record the condition of the lock and contact a specialist.

What the master can check

A specialist can determine:

• does the cylinder correspond to the previous system;
• is there a technical jam;
• is the key damaged;
• is it possible to open it carefully;
• what needs to be repaired after opening.