referring now to the figures of the drawing in detail , material webs which are wound into rolls , in particular household or sanitary paper , generally require , since they are cut from a strand , bearing journals 4 , 5 projecting at the end when they are inserted into guides and are housed rotatable there . the bearing journals 4 , 5 can be provided on the ends of a support rod 1 or on end caps 2 , 3 , which are inserted for example into a cardboard tube 15 . fig1 to 5 show in each case on the left a simple bearing journal 4 with a circular cylindrical rotating surface , which fits into a groove of the guide 20 . in principle however it is also possible to form the bearing journals 4 and the guides 20 also according to one of the possibilities below , described for the bearing journals 5 and guides 21 shown on the right in each case , as the embodiment according to fig7 shows . each bearing journal 5 also has a circular cylindrical rotating surface as bearing surface 8 , which is formed according to fig1 to 4 by the bottom surface of a circumferential groove 7 and according to fig5 and fig7 on the left by the peripheral surface of the end - section 6 of the bearing journal 5 . in order to be able to insert only correctly aligned rolls in the different guides 20 , 21 , constrictions 22 are provided on the guides 21 , through which only correspondingly formed areas of the bearing journals 5 can be passed . the constrictions 22 are formed by projections 25 or the like protruding into the guide 21 , on which first guide surfaces 23 are provided which are preferably formed parallel to the axis of the roll and have increasing initial sections 26 . the constrictions 22 are preferably provided on inserts 28 ( fig7 , 8 ), which can be introduced into the initial area of the guides 21 . on the free ends 11 , the bearing journals 5 have recesses 12 which are formed diametrically opposed to the projections 25 in the guides 21 . the recesses 12 are provided with fitting surfaces 9 which , unlike the bearing surfaces 8 , are not rotating surfaces , but instead in particular flat side - surfaces of end grooves ( fig1 , 2 , 4 , 6 , 7 - right ), of an end bar ( fig5 , 7 - left ), wherein the recesses 12 are formed by the areas on both sides of the bar , or by generated - surface sections 14 if the end - section 6 is prismatic ( fig3 ). as the figures show , the fitting surfaces 9 not formed as rotating surfaces and the first guide surfaces 23 on the projections 25 allow a large number of different combinations , should a coding between the bearing journals 5 and the guides 21 be desired not only so as to insert only correctly aligned rolls but also to prevent the use of the wrong rolls . in addition , as can be seen in fig1 , 2 , 3 and 6 , the diameters of the bearing journals 5 in the area of the bearing surfaces 8 can be greater than the diameters of the left - hand bearing journals 4 , but this is not absolutely essential . there must be sufficient clearance between the bearing journals 4 , 5 and the guides 20 , 21 in order not to jam the rolls in the guides . since the projections 25 in the recesses 12 can be freely moved in the direction of the roll axis , the bearing journals 5 are provided with axial guide surfaces 10 , which cooperate with corresponding second guide surfaces 24 on the guides 21 , in order to prevent the bearing journals 5 from slipping out at least from the guides 21 . the axial guide surfaces 10 are formed on the bearing journals 5 , in particular as shown in the figures , by the side - wall of the circumferential groove 7 nearer the end 11 , in which bars 27 facing each other on the guides 21 engage , to which the second guide surfaces 24 are attached . axial guide surfaces 10 can however also be provided on tooth - like projections or similar protruding from the periphery of the bearing journals 5 , which makes a circumferential groove unnecessary . the axial guide surfaces 10 and the second guide surfaces 24 lie in particular in radial planes of the roll axis , but can also , as shown in fig5 , be conical surfaces . particularly advantageous embodiments are shown by fig2 and fig7 on the right . in fig2 , the depth of the recess 12 is equal to the length of the end - section 6 , so that the bottom 13 of the recess 12 is flush with the side wall of the circumferential groove 7 nearer the free end 11 of the bearing journal 5 . in fig7 on the right the recess 12 also extends into the circumferential groove 7 . both embodiments provide particularly good assurance that only bearing journals 5 in the embodiments shown in fig2 or fig7 on the right can be inserted into the guides 21 shown in fig2 or fig7 on the right , since in both embodiments it would not be possible to shorten the end - section 6 of a bearing journal 5 in order to circumvent the projection 25 in the guide 21 . in this case the axial guide surface 10 would actually be omitted .