noun
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: ものさし
大工さんは尺を使って木材の長さを測った。
The carpenter measured the length of the lumber with a ruler.
ものさし is the more common and explicit word for a ruler or measuring stick. 尺 can be a shorter, more technical or compound form.
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).