An article today on vandalism at a school says that "caulk was placed in door jams."
The vertical posts that make up the sides of a door are jambs, and jamb is frequently confused with its homophone jam.
The word came from Old French into Middle English as jambe from the Latin gamba, "leg" or "horse's hock." The word identified a metal leg piece in armor, and the resemblance to legs evidently led to the word being applied to door posts.
Jamb can also signify the side posts of a window or chimney-piece.
The noun jam, for "a conserve of fruit prepared by boiling it with sugar to a pulp," if you are still interested, likely derives from the verb jam, "to bruise or crush by pressure." The Oxford English Dictionary speculates that its origins are onomatopoeic. And, English being the free-spirited language it is, the word was occasionally spelled jamb.
If identified, the teens responsible for the vandalism will be in a jam.