of the heatable body 11 which is shown on the right hand side of fig1 and extends to the exterior area of housing 10 it allows easy and smooth insertion of the rod 16 made of the binding material and further prevents unnecessary heat loss towards the outside through the right hand end of heatable member 11 as shown in fig1 guide channel 14 is a conical channel whose diameter decreases from the right hand to the left hand side on the left it terminates in a valve unit 17 which has a mouthpiece 18 the latter constituting the actual outlet 19 for the liquefied binding material valve unit 17 includes a one way valve in the form of a ball valve 20 which operates under the control of a spring 21 specifically the valve opens when a predetermined pressure is exerted from the material in guide channel 14 valve unit 17 may also be a die cast aluminum member it may also be manufactured of other material for example brass a second longitudinal channel 22 is provided in heatable member 11 channel 22 extends in a direction substantially parallel to guide channel 14 and is situated below the latter it is also of conical shape and its diameter decreases as does that of guide channel 14 from the right hand to the left hand end channel 22 extends along most of the length of guide channel 14 specifically in the illustrated example it extends over more than three fifths of the length of the latter a ptc positive temperature coefficient resistor cartridge 23 is arranged in the second channel 22 it may be pressed into channel 22 or may be glued or screwed into that channel the ptc resistance cartridge 23 includes a.