An endpiece which forms an integral part of a mandrel used to support a roll of material engages a guide. The endpiece comprises a cylindrical part which can be inserted into the mandrel, a collar which rests against a facing surface of the endpiece, and a projecting attachment. A guiding and retaining groove is provided along the length of the projecting attachment to form a guide path. A cooperating guide is provided on a bracket that supports the roll of material. The guide is disposed on an inner side of the bracket and comprises slightly-projecting flats which form and define a channel to receive the projecting attachment of the endpiece as so enable the endpiece to be inserted and retained therein. The channel extends into a part for receiving the endpiece following the insertion thereof.