Protect wood permanently with clamp pads
Pipe clamps will dig right into the wood unless you put some protection between the jaws and the work. Trouble is, you can't hold the pads in place, align the workpieces, and tighten the clamps with just two hands.
If you attach the clamp pads to the jaws, you won't have to fuss with them when your hands are full. Cut pads similar to those shown to fit your particular clamps. You want the large hole to fit the pipes, yet allow free movement. Drill holes for #6 or #8 sheet-metal screws where indicated, and attach the pads to the clamp jaws. For further protection, glue a leather facing to the clamping area on the pad. The pad design shown offers a bonus, too: The wide bottom allows you to stand the clamps on a bench or sawhorses for easier clamping.
—Hayden C. Jones, Shenandoah, Iowa