Hmmm .... so electricity does have some role to play here too ! Cough cough !

The black box to the left is not a point-machine but a set of moving electrical contacts which in signalling parlance are called "Points and Lock Detector".These are finely aligned switches which operate only if the point and its lock(or lock-bar if...

The black box to the left is not a point-machine but a set of moving electrical contacts which in signalling parlance are called "Points and Lock Detector".These are finely aligned switches which operate only if the point and its lock(or lock-bar if provided)are in their correct position and there is absolutely no gap between the Stock and the Tongue rails.Hence the detector is a very critical safety component of a point.In the case of point-machines the driving,locking and detection assembly is incorporated into a single enclosure.
Here,a key interlocking arrangement has been provided which is in the middle of the rails.Note the removable slide with the handle which must be removed to "swing" the points.This slide probably has a padlocking hasp at the other end.Also note the two keyholes at both sides of the slide which are the actual key interlocks.Logically.their should have been at least one lock with the key inserted but it seems to be missing here.