An apparatus for assembling and hemming fabrics by hot applying strips (5) or films (5) to which thermofusible plastic materials have been applied or spread, comprising, on a bearing framework, a strip or film supplying spool (4), the strip or film being entrained on a pulling roller (7), cooperating with a sensor roller (8) mounted on a swinging lever (9), supporting a strip guiding pawl (13), the strip being further entrained on a strip supply pulling element. Downstream of the pawl (13) a guiding assembly is provided, having an adjustable width, and at the outlet of said guiding assembly, a pressing roller (30) is arranged, which is associated with a foot assembly (31), cooperating with entraining grippers (33, 34) for driving with an indexing type of movement, the fabric materials on which the strip (5) is applied.