This invention relates to such attachment devices between two work pieces, for instance a furniture leg (1) and a frame (2) of a furniture, which consist of a screw (9), which is inserted into a hole in said first work piece and further into a lock washer (5) of a somewhat sagging material, which washer by a slot (4) is divided up into two lock washer (5) portions, which are revolving towards each other around a hinge (6), said hinge has a hole for the end portion of the screw, whereby the shape of the lock washer is such that before the tightening of the screw the lock washer will rest against a wall of the second work piece (2) with two edges (12), which are situated at a distance from the slot (4) and with the hinge situated at a distance from said wall, so that, when tightening the screw, the washer portions (5) will revolve against each other and lockingly press against the screw.
The locking effect will be strengthened by the attachment device according to the invention in that way that the end portion of the screw (9) and the lock washer (5) are placed in a recess (3) in the second work piece (2), so that said edges (12) of the lock washer (5) will rest against surfaces of the wall of the recess, which oppose each other, so that after the tightening of the screw the pressure from said surfaces against these points will cooperate to press the washer portions against the screw.