Lining board with a support with an approximately U-shaped cross section

A form panel (1) with at least one girder (4) which supports a lining skin (2) on a side averted from a concrete location and has an approximately U-shaped cross section comprising U-limbs (5) of said girder connected by a U-crosspiece (6) situated on a side of said girder averted from the lining skin (2), and said U-limbs (5), viewed in cross section, diverging slantwise from the U-shaped crosspiece (6) and each having at free ends oppositely directed fastening flanges (7) which project outwardly from the U-limbs (5) and serve for being applied to the lining skin (2), characterized in that the girder (4) comprises two U-shaped girder portions (4a,4b) which are adjustable relative to each other in a longitudinal direction and comprise an at least partially internal girder portion and an external girder portion which embrace each other at least in an overlapping zone, whereby inside the cross section of the at least partially internal girder portion (4b) of the U-limbs (5) thereof form together with the lining skin (2) an angle of inclination which is more obtuse or larger than that of the external girder portion (4a) embracing the internal girder portion (4b), and that at the lining skin (2) the width between the U-limbs (5) of the internal girder portion (4b) plus the width of the oppositely directed fastening flanges (7) of the internal girder portion (4b) is smaller than that between the U-limbs (5) of the external girder portion (4a) so that when the lining skin (2) is level the fastening flanges (7) of both girder portions (4a,4b) lie side by side in the same plane.