Rolling mill for metal strip comprising: - a retaining cage, - a set of superposed cylinders with substantially parallel axes comprising two working cylinders (3, 4), lower and upper, defining the passage air-gap, and two supporting cylinders (5, 6) respectively lower and upper, intended to respectively bear on the working cylinders of the side opposite that of the passage air-gap, - each cylinder having two ends mounted rotating, each on a bearing carried by a chock (30, 40, 50, 60), - guiding means between the chocks (30, 40, 50, 60) of the cylinders and the retaining cage, along the clamping plane, - means for applying a clamping force between the chocks of the supporting cylinders, comprising hydraulic actuators (Vs), - a system for clamping the chocks (30, 40) of the working cylinders, ensuring the locking of the chocks with respect to the retaining cage, about the axis of the cylinder, while ensuring the sliding thereof of the chocks (30, 40) along the guiding means, along the clamping plane, and wherein the system for clamping the working cylinders comprises mechanical means which could pass from a first retracted position, enabling the removal about the axis thereof of the working cylinders outside of the retaining cage to a second locking position ensuring the locking of the chocks with respect to the retaining cage, about the axis of the cylinder, said mechanical means using: - the convergence movement of the lower cylinders (3, 4) with respect to the upper cylinders (5, 6) during the closing of the retaining cage to lead to the passage from the first retracted position to the second locking position, and - the deviation movement of the lower cylinders (3, 4) with respect to the upper cylinders (5, 6) during the opening of the retaining cage, to lead to the passage from the second locking position to the first retracted position, characterised in that said mechanical means comprise at least one mobile member, sliding along a level of the retaining cage, under the action of the opening or closing movements of the retaining cage, said mobile member extending in length, along a level of the retaining cage, received in a groove in the depth of the inner wall of a level, comprising a locking end, which in said second locking position of the mechanical means, simultaneously penetrates into a vertical groove of one of the chocks of a working cylinder and in the vertical groove integral with the level of the retaining cage to ensure the locking of the chocks with respect to the retaining cage when the locking end is received simultaneously in the two grooves (28, 32) facing one another, belonging respectively to the level and to the chock, and which in the first retracted position of the mechanical means, is retracted by sliding outside of the groove of the chock ensuring the removal of the working cylinder outside of the retaining cage. - a retaining cage, - a set of superposed cylinders with substantially parallel axes comprising two working cylinders (3, 4), lower and upper, defining the passage air-gap, and two supporting cylinders (5, 6) respectively lower and upper, intended to respectively bear on the working cylinders of the side opposite that of the passage air-gap, - each cylinder having two ends mounted rotating, each on a bearing carried by a chock (30, 40, 50, 60), - guiding means between the chocks (30, 40, 50, 60) of the cylinders and the retaining cage, along the clamping plane, - means for applying a clamping force between the chocks of the supporting cylinders, comprising hydraulic actuators (Vs), - a system for clamping the chocks (30, 40) of the working cylinders, ensuring the locking of the chocks with respect to the retaining cage, about the axis of the cylinder, while ensuring the sliding thereof of the chocks (30, 40) along the guiding means, along the clamping plane, - the convergence movement of the lower cylinders (3, 4) with respect to the upper cylinders (5, 6) during the closing of the retaining cage to lead to the passage from the first retracted position to the second locking position, and - the deviation movement of the lower cylinders (3, 4) with respect to the upper cylinders (5, 6) during the opening of the retaining cage, to lead to the passage from the second locking position to the first retracted position,