Richard Hendrickson notes:

"Also, don't forget destination cards, which were stapled onto the
destination card boards (or, on wood sheathed cars, just about anywhere
the car clerks chose to put them, though usually on the doors). These
were small white cardboard tags with destinations either printed or
written on them."

There is a video produced by Mark I Video named Omaha: Rail Metropolis. This video shows a clerk compiling such cards and then yard crews tacking them to various cars. The UP frt conductor's book I have includes the numbers...0-6 [ as I recall ] in the destination column.

Mike Brock