Oil dipsticks are inserted into the engine oil pan to measure oil level, typically accessible from the engine bay. Construction utilizes a calibrated shaft with markings indicating minimum and maximum fluid levels. The tip features a sealing o-ring or flange to prevent oil leakage past the guide tube. Many designs incorporate a handle for ease of removal and inspection, and some feature a wiping surface to ensure accurate readings. Materials are commonly steel, stainless steel, or high-temperature polymers, resisting degradation from engine oil and heat.