Lace card

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A lace card from the early 1970s.
A lace card from the early 1970s.

A lace card is a punch card with all holes punched (also called a whoopee card, ventilator card or IBM doily). Card readers tended to jam when a lace card was inserted, as the resulting card had too little structural strength to avoid buckling inside the mechanism. Card punches could also jam trying to produce cards with all holes punched, owing to power-supply problems. When a lace card was fed through the reader, a 'card knife' was needed to clear the jam.

More modern equivalents include the black fax and computer-based denial of service attacks.