lace card

(Obsolete) A punched card with all holes punched (also

called a "whoopee card" or "ventilator card"). Card readers

tended to jam 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.

[Jargon File]