Obstruction wrenches are a tool used to loosen or tighten stubborn bolts that cannot be accessed with regular wrenches due to the presence of obstructions. These types of wrenches are also known as crowfoot wrenches. Other synonyms for obstruction wrenches include flare nut wrenches, line wrenches, crowsfoot spanner, and angled wrenches. Flare nut wrenches are ideal for use on flare nuts found on fuel lines, brake lines, and hydraulic lines. Line wrenches are similar to flare nut wrenches but have a narrower opening, making them more suitable for tight spaces. Crowfoot spanners are wrenches that have a wide opening with flaring sides, perfect for use in situations where a regular wrench cannot be used. Angled wrenches, on the other hand, have an angled head that allows you to reach bolts in tight or awkward spaces.