the heat engine 1 of the device of the invention consists essentially , on the one hand , of a cylinder 2 , with a centreline 20 , in which a piston 3 , with its rod 32 , is fitted so as to slide in order to drive a fastener through a nose , or guide point , 4 , of the device , and , on the other hand , a combustion chamber 5 , formed at the rear of the cylinder 2 , of a cylinder sleeve 6 , the drive piston 3 and a cylinder head 7 . a fan 8 for stirring the inflammable mixture , draining and cooling , is arranged in the chamber 5 , its electric motor 33 being housed in the cylinder head 7 , beyond which a spark plug ( not shown ) projects into the chamber . in its forward stroke the piston 3 abuts against a shock absorber 34 arranged at the front end of the cylinder . the heat engine is arranged in a casing 9 closed at the rear by a ventilation cover 10 and two shells 11 , 12 of a handle 13 . to be more precise , the casing has four angle grooves such as groove 55 in fig2 and 3 , ending at the rear with four supporting shoulders 14 , 17 , in each of which a smooth bore is drilled to take , driven through the bores , four bolts 21 - 24 for fixing the cover 10 and the handle shells 11 , 12 , the bolts being screwed into two pairs of tapped angle stiffeners such as the stiffener 56 in fig3 , formed at the rear of the shells , on their inside wall , these stiffeners being housed in the grooves 55 of the casing , supported against the shoulders 14 - 17 . the angle stiffeners 25 - 28 at the rear of the shells can retain the cylinder head 7 in certain instances . each of the handle shells has a pierced frame 36 ( 37 ) designed to be laid against a side wall 38 ( 39 ) of the casing and , at the rear , a semi - flange 40 ( 41 ) to improve the rear covering of the casing by the two semi - flanges joined , by tongue and groove , as a fixing sleeve 42 . each shell is extended at the rear by the real handle part 43 ( 44 ) and , at the front , by a housing or supporting structure 45 ( 46 ), either for an electricity supply battery or for a fasteners charger . therefore , the engine 1 is arranged in the casing 9 which is fitted into the assembly of the two shells 11 , 12 of the handle 13 to which it is fixed at the rear by the bolts 21 - 24 . on their inner surface 46 , at the bottom near the handle 43 , 44 , the shell cheeks 36 , 37 carry , from the same castings , small annular funnels , oblong in section , one 47 at the rear and another 48 at the front . fig3 shows only the inside surface and the funnels of the left side cheek 37 . as will already have been noted , the fixing arrangement has a plane of symmetry going through the centreline 20 . the side walls 38 , 39 of the casing 9 , in positions corresponding to those of the funnels 47 , 48 , therefore at the bottom at the front and at the rear , also have , from the same casting , small annular funnels 49 , 50 , also oblong in section , designed to work in conjunction by fitting into each other , like tenons and slots , with the funnels 47 , 48 of the shell cheeks 36 , 37 . fig3 shows only the funnels 49 , 50 of the side wall 38 of the case 9 . the rear tenons and slots 49 , 47 , more of less with the same inside and outside sections , fit overall more or less by force fitting into each other . on the other hand , the front tenons and slots 50 , 48 , fit into each other with a slight force fit in their cross dimension but not in their dimension parallel to the centreline 20 . in other words , the outside axial length of the tenons 50 of the front part 91 of the case 9 is appreciably shorter than the inside axial length of the slots 48 , specifically to enable axial sliding of the tenons in the slots . thus , the front 91 of the case 9 is fitted floating in the handle 11 - 13 and can slide in it along the drive axis 20 of the fasteners . of course , the respective arrangements of the tenons and slots could be reversed , the tenons forming part of the casting of the handle shells . in all cases , the front tenons are shorter than the front slots . the front 51 and rear 52 annular walls of the front funnel slots 48 act as front and rear stop parts for the front tenons 50 of the case .