Abstract: Smooth and uniform concrete floor or roof sections of channel formation with metal reinforcement are produced by linear movement of a slip form guided by relatively stationary rails which mold the side faces of the channel sections. Skid members which follow the rails also serve to mold the top linear edges of the concrete channel sections. The proper placement of a welded reinforcing grid is achieved by a forward adjustable template and the wall thickness and internal radii of the molded channel are established by a rearward adjustable template. The cooperating templates provide a concrete hopper structure on the slip form.