Braided steel lines are a type of brake part that attempts to remedy some of the problems associated with solid steel brake lines. In a braided steel brake line, a soft brake line is encased in a mesh made of braided strips of steel. You can think of it as a long, thin steel basket. This type of line is sometimes used in household plumbing applications, too. In fact, if you take a look under your kitchen sink, you just may see some braided metal lines.
Because the braided steel mesh has more give than hard steel tubing, the connections for braided brake lines aren't as stressed. At the same time, the braided steel protects the line encased within and prevents swelling. Another plus is that braided steel lines are very attractive. For a lot of hot rodders and classic car buffs who "dress" their car's engine compartment by adding components that look good and well as improve performance, braided steel lines are a must to go with the chrome air filters, valve covers and exhaust headers already in the engine bay.
Because the soft tubing is encased in braided steel, you can't visually inspect the lines for leaks or corrosion. While this is fine for racecars or even off-road vehicles that have these brake parts replaced often, it can be a problem for most street cars. You might not know you have a problem until it's too late. Regular brake system maintenance is critical when you're using braided brake lines.