Hobbies Cars & Motorcycles What Is a Line Wrench? A Very Useful Mechanics Tool Share PINTEREST Email Print Use a line wrench on brake lines, gas lines, or adjustable cables. photo by Matt Wright, 2008 Cars & Motorcycles Cars Basics Buying & Selling How Tos Reviews Tools & Products Classic Cars Exotic Cars Corvettes Mustangs Tires & Wheels Motorcycles Used Cars SUVs Trucks ATVs & Off Road Public Transportation By Matthew Wright Matthew Wright has been a freelance writer and editor for over 10 years and an automotive repair professional for three decades specializing in European vintage vehicles. our editorial process Matthew Wright Updated March 22, 2017 If you are working with any type of fitting that is in-line - such as a brake line, fuel line, or any type of cable - a line wrench can be a life saver. Standard open end wrenches may not grip the hex well enough, which can lead to stripping - a real pain in the neck! To use a line wrench, just slip the open part of the wrench over the line, then slide it onto the hex part of the fitting.