Abstract: In an automatic device for the insertion of small blocking strips or ribbons adapted for the insertion in the groups of mating holes of material consisting of laterally punched and coupled sheet groups, whereby each strip takes a U-shaped configuration and is fixed to the first and to the last sheet of the sheet group by means of adhesive areas provided in the strip itself, an improved structure of small strip inserting device, by which each small ribbon is cut from a continuous ribbon and inserted into position without special operation carried out on the receiving holes.