Rudding is a sexual act mainly performed by Scottish Sailors which involves penetrating your sailing partner with an oar and using them to steer the boat. Double rudding is where you also put an oar in their mouth.
Some extremists prefer to stimulate their sailing partners by rubbing them against a working rudder, this is not reccommended as genital mutilation occurs in most instances.
"Man Hagrid, I'm so horny. Won't you give me a good rudding?"