When clamps are tightened, the pressure that’s concentrated at the jaws will often mar the surface of the workpiece. Distributing this pressure will greatly reduce the damage, so woodworkers often insert a block of scrap wood, called a clamping block or clamp pad, between the clamp jaws and the workpiece. These wooden clamping blocks work pretty well, but it usually takes three hands to hold the two pads in place while tightening the clamps. More often than not, the blocks end up on the shop floor before you secure the clamp.
There is an easier way. Use a hot-glue gun to “cement” the clamp block to your jaws. The pads stay firmly in place for your clamping jobs, but can be removed (and the glue peeled off) with a minimum of effort.