Katko isolator handles have two different features: door interlocking and defeat mechanism, to help assist with inspection and fault finding.
The door interlocking feature on the Katko enclosed isolators and panel mounted isolators makes sure the cover/door stays closed, when the switch is in ON-position.
However, in ON-position, the defeat mechanism allows the cover/door to be opened by sliding the red part with a tool, such as a flat head screwdriver (see video below).
Opening in ON-position is important for measuring reasons (making sure the installation works as planned or when finding out faults).
When the handle is in the OFF-position, the cover can be opened.
However, to install padlocks, the red defeat mechanism needs to be slid to open the holes for the padlocks and at the same time this mechanism prevents against the cover being opened.
So, when locks are on, the switch cannot be turned ON and the cover cannot be opened.
These features are critical when it comes to safety and should only be carried out by trained industry professionals.