Most of the security door locks used today are profile cylinders.
They can be locked from both sides with the appropriate key. The most common profiles are the EU tap profile and the round cylinder (mainly used in Switzerland).
Profile cylinders can be equipped with additional features beyond the usual function of locking.
These include the drilling and Core pulling protection. In addition, most profile cylinders can be equipped with a Emergency and danger function. A key can be inserted on the inside of the cylinder and it can still be unlocked from the outside.
At KESO, for the emergency and danger function, which is only realized with special keys, there is as a supplement the Priority function.