... .Roller :anti-noise nylon roller ,reduce friction with ground.Lock system :1.multi cross shafts,using solid core square steel and ... 4 sides safety.2.Automatic locking system :while close the box , automatic locking system will lock the box immediately .3.Automatic re ... by improper way or force ,box will re-lock itself.4.Password lock ,mechanical lock ,which is drill-proof ,smash-proof ,technically ...