A measuring tool, often a straight ruler or tape measure. The cross-reference to ものさし suggests it may be a shorter form or used in compounds.
See also: 物差し
The carpenter measured the length of the lumber with a ruler.
Standard kanji spelling for this meaning.
Alternate kanji spelling, less common than 尺.
Rare alternate kanji spelling.
The kanji 尺 originally referred to a traditional unit of length (about 30.3 cm) and by extension came to mean a ruler or measuring tool. The reading さし is likely related to the verb 差す (to point, to measure).