A vertical vacuum furnace assembly comprising: a vertically oriented pressure/vacuum vessel having an opening at a lower end thereof; a bottom head assembly dimensioned for closing the opening in said pressure/vacuum vessel; a support structure consisting of first and second preassembled leg assemblies (16, 18) arranged on opposite sides of said pressure/vacuum vessel and having support arms (40a-40d) attached to said pressure/vacuum vessel; and a control system; wherein each of said preassembled leg assemblies comprises: first and second columns (32a, 32b); a floor plate connected to the bottom ends of the first and second columns for attaching said columns to a surface; a cross beam connecting the first and second columns in spaced relation to each other, said cross beam being positioned at a first distance above said attaching means; first and second guide channels (42a, 42b) affixed longitudinally to the first and second columns on facing surfaces of said first and second columns between the attaching means and the cross beam; a trolley movably disposed in said first and second guide channels; and a reversible lifting mechanism supported on said cross beam, mechanically connected to said trolley for lifting or lowering said trolley, and electrically connected to said control system whereby said reversible lifting mechanism can be operated to lift or lower said trolley. a vertically oriented pressure/vacuum vessel having an opening at a lower end thereof; a bottom head assembly dimensioned for closing the opening in said pressure/vacuum vessel; a support structure consisting of first and second preassembled leg assemblies (16, 18) arranged on opposite sides of said pressure/vacuum vessel and having support arms (40a-40d) attached to said pressure/vacuum vessel; and a control system; wherein each of said preassembled leg assemblies comprises: first and second columns (32a, 32b); a floor plate connected to the bottom ends of the first and second columns for attaching said columns to a surface; a cross beam connecting the first and second columns in spaced relation to each other, said cross beam being positioned at a first distance above said attaching means; first and second guide channels (42a, 42b) affixed longitudinally to the first and second columns on facing surfaces of said first and second columns between the attaching means and the cross beam; a trolley movably disposed in said first and second guide channels; and a reversible lifting mechanism supported on said cross beam, mechanically connected to said trolley for lifting or lowering said trolley, and electrically connected to said control system whereby said reversible lifting mechanism can be operated to lift or lower said trolley. first and second columns (32a, 32b); a floor plate connected to the bottom ends of the first and second columns for attaching said columns to a surface; a cross beam connecting the first and second columns in spaced relation to each other, said cross beam being positioned at a first distance above said attaching means; first and second guide channels (42a, 42b) affixed longitudinally to the first and second columns on facing surfaces of said first and second columns between the attaching means and the cross beam; a trolley movably disposed in said first and second guide channels; and a reversible lifting mechanism supported on said cross beam, mechanically connected to said trolley for lifting or lowering said trolley, and electrically connected to said control system whereby said reversible lifting mechanism can be operated to lift or lower said trolley.