Dipstick

A gage, made in the form of a thin metal rod, used to measure the level of a liquid in a reservoir. The dipstick is pushed into the reservoir until it contacts a built-in stop; then it is removed and visually inspected. The level of the liquid in the reservoir is indicated by the amount of the dipstick wet by the liquid. A dipstick is the normal method used for measuring the amount of lubricating oil in the sump of an engine and the amount of hydraulic fluid in a reservoir.