Method for converting a single-strand continuous casting plant for slabs into a multi-strand continuous casting plant for billets, wherein the continuous casting plant for slabs comprises - a mould for casting liquid steel into a slab strand and an oscillating unit for oscillating the mould; - a strand guide for supporting, guiding and cooling the slab strand, wherein the strand guide has a plurality of hydraulically adjustable segments (4a...4n) the slab strand is cooled in the segments (4a...4n) by cooling nozzles and, where appropriate, reduced in its thickness, and the segments (4a...4n) are mechanically connected to a rear construction and fluidically connected to in each case a hydraulic supply and a water supply; comprising the following method steps: i) decoupling the water supply from the mould and decoupling the hydraulic supply from the oscillating unit of the continuous casting plant; ii) removing the mould and the oscillating unit and installing a common support frame for a plurality of billet strands in the region of the machine head of the continuous casting plant, wherein the common support frame is connected to the main body of the continuous casting plant; iii) installing in each case one mould for casting liquid steel into a billet strand and in each case one oscillating unit for oscillating the mould per billet strand, wherein a plurality of oscillating units are connected to the common support frame; iv) coupling the water supply to the moulds and coupling the hydraulic supply to the oscillating units; v) decoupling the water supply and hydraulic supply from the segments (4a...4n); vi) releasing the segments (4a...4n) from the rear construction of the continuous casting plant and removing the segments (4a...4n) from the continuous casting plant; vii) connecting roller pairs (104a...104i) for guiding a plurality of billet strands to the rear construction, wherein the billet strands are supported on both sides by a roller pair (104a...104i) and cooled by cooling nozzles; viii) coupling the cooling nozzles of the roller pairs (104a...104i) to the water supply; ix) connecting at least one extraction unit for extracting a plurality of billet strands from the moulds to the rear construction; x) coupling the extraction unit to the hydraulic supply. - a mould for casting liquid steel into a slab strand and an oscillating unit for oscillating the mould; - a strand guide for supporting, guiding and cooling the slab strand, wherein the strand guide has a plurality of hydraulically adjustable segments (4a...4n) the slab strand is cooled in the segments (4a...4n) by cooling nozzles and, where appropriate, reduced in its thickness, and the segments (4a...4n) are mechanically connected to a rear construction and fluidically connected to in each case a hydraulic supply and a water supply; i) decoupling the water supply from the mould and decoupling the hydraulic supply from the oscillating unit of the continuous casting plant; ii) removing the mould and the oscillating unit and installing a common support frame for a plurality of billet strands in the region of the machine head of the continuous casting plant, wherein the common support frame is connected to the main body of the continuous casting plant; iii) installing in each case one mould for casting liquid steel into a billet strand and in each case one oscillating unit for oscillating the mould per billet strand, wherein a plurality of oscillating units are connected to the common support frame; iv) coupling the water supply to the moulds and coupling the hydraulic supply to the oscillating units; v) decoupling the water supply and hydraulic supply from the segments (4a...4n); vi) releasing the segments (4a...4n) from the rear construction of the continuous casting plant and removing the segments (4a...4n) from the continuous casting plant; vii) connecting roller pairs (104a...104i) for guiding a plurality of billet strands to the rear construction, wherein the billet strands are supported on both sides by a roller pair (104a...104i) and cooled by cooling nozzles; viii) coupling the cooling nozzles of the roller pairs (104a...104i) to the water supply; ix) connecting at least one extraction unit for extracting a plurality of billet strands from the moulds to the rear construction; x) coupling the extraction unit to the hydraulic supply.