Sizing rings up, involves cutting the bottom of the shank, pulling the two sides apart, building a bridge of new gold based on the size needed and then soldering it in - preserving the thickness at the base of the ring, where it is most essential.
Sizing rings down, is accomplished by cutting the bottom of the shank, taking out the proper length of gold and soldering the two pieces back together.
One concern that customers tend to have relates to the integrity of the side stones after a ring has been resized either up or down. The stones are always checked before sizing; if any of them are loose, they are tightened before continuing. This ensures that none of them will be compromised during and after the process.