the auxiliary locking device illustrated in fig1 is in the form of a box of moulded synthetic material , for example of polystyrene of virtually uniform thickness . this box , of general rectangular shape , comprises a front vertical wall 1 , two vertical side walls 2 and 3 , a lower horizontal wall 4 , an oblique wall 5 connecting the front wall 1 to a vertical back wall 6 parallel to the wall 1 . the wall 6 comprises two vertical rectangular lugs 7 and 8 . the side walls 2 and 3 each have a boss 9 , respectively 10 , constituted by a ramp starting from the edge of the wall in the direction of the front wall 1 , which ramp is followed by a face parallel to the front wall 1 . fixed in this front face 1 is a lock 11 which can be actuated by a key 12 and whereof the bolt 13 , able to rotate about a horizontal axis , may emerge from the box through a cut - out 14 provided in the horizontal wall 4 . in its front face 15 , the drawer intended to receive the auxiliary locking device comprises a rectangular housing 16 whereof the dimensions are identical to the dimensions of the locking device , naturally with a slight clearance making it possible to introduce the locking device easily into its housing . this housing 16 is limited by a vertical base 17 , two vertical side walls 18 and 19 , an upper horizontal wall 20 and a lower horizontal wall 21 . the upper wall 20 comprises two rectangular cut - outs 22 and 23 . the side walls 18 and 19 comprise a rectangular cut - out 24 , respectively 25 . in the sectional view shown in fig2 it can be seen that the front part of the drawer has a constant wall thickness and that it is constituted by a profiled part supporting the side wall 18 to 21 of the housing 16 and oblique facing walls such as 26 and 27 , the back wall 17 of the housing being integral with the drawer proper to which the said profiled part is welded . a small tongue 27 is cut in the lower horizontal wall 21 , which small tongue is connected to the wall by a thin part 28 and supported by a rib 29 of the wall 17 . a space 30 is left opposite the small tongue 27 , between a part of the edge of the oblique wall 26 and the wall 17 . in order to fix the auxiliary locking device to the drawer , the small tongue 27 is first of all bent upwards , in the direction of arrow f ( fig2 ) by introducing a knife or screwdriver into the slot 30 . the small tongue 27 is either simply bent through 90 ° or completely detached , in order to clear the passage for the bolt 13 of the lock . the auxiliary locking device is then introduced obliquely into the housing 16 , thus engaging the lugs 7 and 8 in the cut - outs 22 and 23 . one then presses on the front face 1 of the auxiliary device in order to force - fit the bosses 9 and 10 between the side walls 18 and 19 of the housing . the elasticity of the walls readily allows this introduction . once at the bottom , the bosses 9 and 10 engage and are fixed in the cut - outs 24 and 25 . the auxiliary device is thus fixed and locked to the drawer , its front face 1 being in the plane of the front face 15 of the drawer . the cut - out 14 of the auxiliary device is thus opposite the cut - out cleared by the bending of the small tongue 27 and the bolt 13 may rotate and project through the slot 30 in order to engage in a keeper 31 integral with the cabinet 32 in which the drawer slides ( fig3 ). numerous variations are possible without diverging from the scope of the invention . the lugs and bosses of the locking device could in particular be located on other sides , in the same way as the bolt of the lock . it will also be possible to eliminate the lugs 7 and 8 and to add a boss such as 9 and 10 on each of the faces 2 and 3 for fixing the auxiliary device solely by means of these bosses . it would even be possible to fix the device by means of only two bosses or by means of a lug on one side and a boss on the opposite side . it would also be possible to dispense with the rib 29 and to make the thin portion 28 so thin that it is able to be bent downwards by the action of the bolt at the time of the first operation of the key . moreover , the lock support must not necessarily be in the form of a box , but it could be flat , i . e . constituted by a rectangular panel fixed for example by lugs provided on two of its opposed sides engaging in cut - outs provided in the side walls 20 and 21 , in the vicinity of the front face 15 .