It sits between three vertically stacked contactors and physically blocks the opposing armature from sealing when one side is already pulled in. No electrical logic, no aux contacts involved; the interlock is pure mechanical gating.
Which contactors it fits
This interlock is specced for a specific stack: bottom position takes LC1F115 through LC1F150 (3P or 4P) or CR1F150 (3P or 4P); middle position takes LC1F265 through LC1F330 (3P or 4P) or CR1F265 (3P or 4P); top position takes LC1F630 (3P or 4P), LC1F800 (3P), or CR1F630 (3P or 4P). If your contactor frame doesn't fall in that list, this interlock won't align — the mounting holes and armature geometry are specific to those TeSys F frames.