Method of manufacturing a folder (1), which continuously or intermittently is fed through a machine (51) by a conveying means (52, 53) adapted to an ordinary folder of a nominal width dimension (Bnom), wherein said folder (1) features an under-dimension in relation to the width dimension of the ordinary folder, and that said folder (1) is placed in a cassette (40) having a dimension (Bk) corresponding to said under-dimension and having an outer dimension corresponding to said nominal dimension (Bnom), which cassette (40) is moved through the machine (51) by said conveying means (52, 53). As well as a machine (51) and a cassette (40) for the realization of said method.