n. obs. A
punched card with all holes punched (also
called a 'whoopee card'). Card readers jammed when they got to
one of these, as the resulting card had too little structural
strength to avoid buckling inside the mechanism. Card punches
could also jam trying to produce these things owing to power-supply
problems. When some practical joker fed a lace card through the
reader, you needed to clear the jam with a 'card knife' --
which you used on the joker first.