the device 10 illustrated in fig1 and 2 the device 10 u2032 in each case has projections 82 standing out from the legs 16 or respectively 18 in the direction of the roller 50 which constitute a lock against rotation whenever the device 10 u2032 is clipped onto a rod like body 62 which has a relatively round profile in the third embodiment of a device 90 according to the invention illustrated in fig7 and 8 the latter likewise has as described in connection with fig1 and 2 a clamp 92 on which an arm 94 is attached pivotably about an axis 98 here too the arm 94 bears a roller 96 by comparison to the device 10 illustrated in fig1 and 2 here the arm 94 can pivot freely and not against the force of a spring neither is a catch provided here such that the operator is free to press the arm 94 or respectively the roller 96 onto the thread using force he chooses this variant is to be employed if the operator actually does want this method that is to say if the operator him herself would like to determine how much pressure is to be exerted by the roller 96 on the thread the device of fig7 and 8 can also accordingly be clipped onto a device illustrated in fig3 fig8 shows that the peripheral surface 100 is provided universally with a lining 102 of a material with a high friction for example a band made of silicon rubber as is evident from the plan view of fig5 the thread 70 is guided in a gutter 74 such.