10 this is accomplished by the use of the articulation member 80 the articulation member 80 is a self contained device that is designed to be fitted between two screed roller members 12 the placement of the articulation member 80 in this manner allows the connected screed roller members 12 to vary in their longitudinal axis with respect to one another thereby allowing the present invention to finish a concrete slab that contains either a central ridge or valley to accomplish this a center support 82 is positioned in the desired location at the longitudinal center of the concrete forms 14 the articulation member 80 is then positioned between two or more screed roller members 12 in a location that it corresponds in its relative location to the center support the articulation member 80 then rides along the top of the center support 82 the height of which relative to the concrete forms 14 determines the rise or drop in the finished concrete 39 s 18 surface the articulation member 80 contains three primary components that make this possible the first of these is a centrally located u joint 98 that is fixedly attached at either end to the other two components the female and male articulation bodies 81 and 83 the u joint 98 employed in this application is of a type that is commonly in automotive or other vehicle applications and allows the two screed roller members 12 to rotate around slightly different longitudinal axises the u joint 98 is located in a centrally located u joint cavity 100 of the female and male articulation bodies 81.