SENTRY n.
Guard; watch, as by a sentinel. Here toils, and death, and death's half-brother, sleep, Forms terrible to view, their sentry keep. Dryden. Sentry box, a small house or box to cover a sentinel at his post, and shelter him from the weather.
SHAFT n.
The slender, smooth stem of an arrow; hence, an arrow. His sleep, his meat, his drink, is him bereft, That lean he wax, and dry as is a shaft. Chaucer. A shaft hath three principal parts, the stele [stale], the feathers, and the head. Ascham.
SIT v.
good preaching. -- To sit up, to rise from, or refrain from, a recumbent posture or from sleep; to sit with the body upright; as, to sit up late at night; also, to watch; as, to sit up with a sick person. "He that was dead sat up, and began to speak." Luke vii. 15.