A joint is provided for articulately interconnecting the adjacent ends of rail assemblies in a tenter frame. The rail assemblies are arranged consecutively along a guide path, and have parallel guide channels for the advancing and returning legs of continuous chains carrying the clamps that grip the edges of the webs being transversely stretched. The joint includes flexible bands arranged to define intermediate channels connecting the guide channels of the rail assemblies. The flexible bands are resiliently deflected in response to articulation of the rail assemblies to thereby arcuately configure the outer medicate channels.