DC......
Sorry I can't really answer that with any sincerity.
Some RFM's talk about frictions and others about locks.
In this instance its "Locks" in the legislation.
Dzeroplus...gave us a dictionary description of locks on page 2.
Over to you....I post on this rather restrictive topic in order to educate Rotorheads as to their liabilities and responsibilities if you go outside the law, regardless if its a conventional wisdom procedure or not!!