1. They should be no foreign, mixing, and they must be separated
2. The total length of the screw should be less than 3 times the diameter of the screw head.
3. The thread of the screw is different. There is a triangular tooth self-tapping locking screw. It has the same pitch and angle as the metric thread, but the section is a triangle, with D and C values 2 parameters that control the locking.
4. It is general determined by the size of the lock mouth.
If the screw is too long, the lock mouth will be inserted, as the lock mouth becomes larger and becomes difficult to lock.
