Personally I am not a fan of this technique:
It only works once the dreadlock roots are already on their way because it cannot be effectively used on super longer, loose roots.
It can make your scalp sore from all the rubbing.
Long term rubbing at your roots can cause damage and root thinning.
It's arguable how effective the root rubbing is for locking at the roots over the long term.
But most dreadheads give clockwise root rubbing a try at some point in the dreadlock-lifetime and some people do swear by it in certain situations and it's less harmful overall than interlocking (-less harmful than attempting to use the interlocking method on non-interlocked dreadlocks.) So for the sake of providing a complete guide to dreadlock maintenance this method is included.