Jamieson, Fausset and Brown on Exodus 39:3

3. cut the gold into wires to work it--that is, the metal was beaten with a hammer into thin plates, cut with scissors or some other instrument into long slips, then rounded into filaments or threads. "Cloth of golden tissue is not uncommon on the monuments, and specimens of it have been found rolled about mummies; but it is not easy to determine whether the gold thread was originally interwoven or subsequently inserted by the embroiderer" [Taylor].