Do not fold, staple or mutilate

The New Wonder Book Cyclopedia of World Knowledge.  Philadelphia & Toronto:  
International Press, 1954.

"Census clerk in Washington, D.C. slips a punched card into a Hollerith tabulating machine during the 1890 count.  Each hole in the card permits a pin to slip through into a socket below, completing an electric circuit and registering one unit on the corresponding dial."  From:  Those Inventive Americans.  National Geographic Special Publications Division, 1971.

As the above images indicate, punch cards have been around for quite a long time.  They really came into their own in the 1970's, when all kinds of information was collected in this form:

 

At Queen's University, Kingston in the 1970's, even student cards were made in this form:

Carefully punching or cutting additional holes in them was a source of amusement for some people, as apparently this could cause havoc with the card readers.