Vise-Grip makes a series of locking wrenches, the 4LW, the 7LW and the 10LW. They are outstanding adjustable wrenches. Picture a standard Vise-Grip with a 60-degree notch cut into the fixed jaw. The wrench clamps down on three flats on a hex-head bolt or nut, enabling the user to apply force with no danger of rounding or slippage. My favorite of the bunch is the 4LW, which is the best flare nut tool I've ever used. Not long ago I used mine to help a friend change the brake hoses on his '72 250C. I'm sure the hoses were original. Each broke free with a loud crack under considerable force, and I didn't kink a line or even distort a flare nut surface. I have never been so impressed with a tool.