Enjambment

Sylvia's sister was always beseeching her to keep her legs together.  Like in nursery school when they sat beside each other on the little plastic chairs that were horribly uncomfortable and hard to stay on without slipping out.  Sylvia would plant her feet firmly on the floor, one either side of the chair, and by barely sitting at all, but almost standing, could be bolt upright whenever Miss Snippet walked past.  Fergie, her sister, however would poke Sylvia and tell her to keep her legs together.  This despite that Miss Snippet was forever dragging Fergie into the naughty corner for not sitting upright and properly on her chair.  When they went home, Fergie would sob to their mother, telling her that Sylvia hadn't been ladylike, and Sylvia would find herself on the naughty step for the evening.
It was eight years before Sylvia discovered that naughty was a word in its own right, and just part of a compound -step or -corner.
In senior school Fergie's insistence that Sylvia keep her legs together grew ever more histrionic as Sylvia became interested in boys and boys became interested in Sylvia.  Not a day would go by without Fergie nagging Sylvia for sitting splay-legged on the bus, for sitting unlike a lady in class assembly, or for acting like a shallot in drama class.  Fergie hinted that she was an appropriate rôle model for Sylvia, that she was an ideal of decorum.
Sylvia looked shallot up in the dictionary and puzzled over it for a while until they read Chaucer in English and she realised what Fergie had meant to call her.
"Keep your legs together!" hissed Fergie from the seat behind Sylvia's on the coach-trip to go Skiing in the Val d'Isere.  Sylvia put her headphones on and tried to ignore her sister.
"Keep your legs together!" read the note that Fergie slipped into Sylvia's pocket while Sylvia was chatting to Gareth in the bar at the ski lodge, both pretending to be over eighteen.  Sylvia found it only after she was dressing again, and since she was leaving Gareth's room to go back to her own she decided to stop by Fergie's on the way and tell her what she thought of her notes.  When she quietly, and unnoticed, walked in on Fergie and Adele she backed out again, leaving Fergie's note in her coat pocket for her to puzzle over and worry about.  'Keep your legs together, indeed!' she thought.
"Keep your legs together," said Mr. Graham, the gynacologist, and Sylvia lifted her head and stared at him.
"What?" she said, nonplussed.
"Er, well," said Mr. Graham taking his half-moon glasses off and cleaning them studiously.  "It's a message from your sister."
"Fergie died," said Sylvia.  "In your offices, of some peculiar bacterial infection.  Two months ago."
"Syphilis," said Mr. Graham polishing harder.  "In that chair, in fact, but don't worry, I've had it wiped down since."
"She's still dead," said Sylvia, shuddering.
"Ye-e-es," said Mr. Graham.
"What?"
"It's her will," he said.  "I have to tell you to keep your legs together every visit."
"That's going to make these examinations difficult then," said Sylvia.  "Shall we try it out?"