Jackknife
Jackknife may refer to:

Pocket knife or jackknife, a compact, foldable knife
Jackknife Bar, Portland, Oregon, U.S.
Jackknifing, a type of crash with articulated vehicle combinations

Film and television
Jacknife, a 1989 American film by David Jones
"Jack Knife", an episode of NCIS
Jackknife, a character on Superjail!

Athletics and sports
Jackknife (exercise), an abdominal exercise
Jackknife, a kicking move involving 540-degree rotation
Jackknife, a type of high dive
Jackknife hold, a pinning move in professional wrestling

Other uses
Jackknife (statistics), a resampling technique in statistics
Jackknife clam, common name for several species of bivalve mollusc

See also
Jackknife Bascule Bridge, a bridge in Thunder Bay, Ontario, Canada
The Jack-Knife Man, a 1920 film