Fixture screw has shaft with one threaded end and head with grip surfaces, midway between which is a cardan joint

摘要

One end of the screw's shaft (1) has a threaded end (2), and the other end has a screw-head (3). Between the thread and the screw head, along the shaft, is a rotarily immovable cardan joint (5) which does not jut out beyond the shaft's cross-section. The screw head has grip surfaces (4) for a spanner.