If you are doing intricate or laborious work that requires both hands, you will need to get a bench vise. The vise has two jaws that firmly hold metal in place. The jaws are tightened by a rod that is turned. Ideally, the jaws should be covered in rubber to avoid marring the jewelry being held. The vise is anchored onto a bench or table by clamps.
Amazon has a bench vise for sale on its website that suctions into place. But, if you are going to do vigorous work, stick with the one that clamps into place. Rio Grande has vises for sale on its website too. They have a vise which revolves so you can work from any angle.