In 1952 routing card boards were to be located on house cars on one door on each side directly under placard board and as near the bottom of door as lifting handle would permit. This followed a circular letter in 1950 to car owners pointing out difficulties utilizing routing card boards which were located higher than 72" above ground level on house cars.

Only routing card boards were lowered. The Car Construction Committee attempted lowering the placard boards as well, but needed approval from the Bureau of Explosives, which would not be granted until 1953. This was also agreed by union carmen and others affected.

Finally, in 1953 agreement was reached to also lower placard boards, to go into effect in 1954.Bob Chaparro
Hemet, CA

It is also worthwhile to note that receptacles for defect cards were required for all cars built new or rebuilt on or after January 1, 1937.  This was to separate defect cards from route cards, which apparently caused some confusion.
Bob Chaparro
Hemet, CA