A ribbon-type device effects undulation of a curtain for gathering the same in the vertical or horizontal direction. A functional unit comprises two tapes of fabric, each of which extends in an undulating manner to form a plurality of alternating positively and negatively curved arcs. An arc of positive curvature of a first fabric tape is set so as to oppose an arc of negative curvature of a second fabric tape and an arc of negative curvature of the first fabric tape is set so as to oppose an arc of positive curvature of the second fabric tape. The two fabric tapes are joined to each other at each transition between an arc of positive curvature and an arc of negative curvature by means of tie-off stitching (tie-offs). A plurality of such tie-offs accommodate a pull cord of a curtain.