Movie funnyman Jack Black is struggling to keep his obsessive compulsive disorder under control - he even instructs friends on how to knock on his door.

The KING KONG star insists on "round numbers" and "clean lines", and hates it when visitors to his home ignore his quirks.

He explains, "I like to knock on a door three times. If someone knocks on a door four times, I don't like it."

Black accepts he infuriates his friends with his Obsessive Compulsive Disorder (OCD) problems - he can't even bring himself to invite them to Tenacious D concerts.

He adds, "If we perform, I can't invite anyone. I can't call because, in my mind, I'm saying, 'It's going to be good enough that you should come down and see me because I'm going to be good tonight,' and that's a jinxer.

"So I don't invite anyone, and people consequently get mad at me."