This was a major improvement on previous non-stepped designs such as the de Bange system, which had only a single thread step and hence only half of the block's circumference had a thread which engaged with the breech, necessitating a fairly long screw to achieve a secure lock.
22.
When opening up your laptop, remove the easily removable parts first : battery, hard drive, DVD drive, and taking special note of where things are connected and what holes screws came out of ( keep notes . . . they sometimes vary in length and putting a too long screw into the wrong hole can be disastrous ).
