curvature which is substantially equal to that of a front concentric bend of the carding engine a plurality of stud bolts are detachably mounted on the upper surface of the base member 4 bolt holes 6 are made at both ends of the base member 4 the stationary flat 8 is formed by placing a plurality of top bars 1 in parallel and extending between two base members 4 the holes of the brackets 3 of said top bars being freely movable on upstanding stud bolts 5 on said base members and adjusting nuts 7 are threaded on the stud bolts 5 above and below the brackets 3 thus making it possible to adjust the vertical position of the top bars 1 by turning the adjusting nuts arms 9 are fixed to both sides of a stationary flat 8 by bolts 10 to form a stationary flat unit 11 in the above embodiment the base member 4 is formed of two members but may be formed of only one member having an opening for fitting the top bars into the central part thereof by this arrangement rigidity of the base member 4 is improved and warp is lessened with the result that stationary flats of more accuracy of gauge.