This is a plunger lock,used for interlocking and securing the points in the correct position.While this is a single-plunger type lock,there are also double-plunger types which can be required for more complex interlocking functions.The key which is...

This is a plunger lock,used for interlocking and securing the points in the correct position.While this is a single-plunger type lock,there are also double-plunger types which can be required for more complex interlocking functions.The key which is removed from this type of lock is then reinserted in another point or a lever to operate another function or to take-off a signal.