[kazinator]

People who say "duck tape" today are mishearing "duct tape", and not referring to a water-resistant, non-sticky wrapping from the 19th century.

Duct tape (the non-heat-resistant, flammable type) is in fact used for ducts anyway.

[ndsipa_pomu]

Not necessarily as Duck Tape is a well known brand in the UK. Also, using it for ducts is prohibited in California and by building codes in other places (according to Wikipedia).