To start a tuberide from behind an already-dropping section; that is, a section breaking ahead of the curl line, but not so far ahead as to make the wave an impossibility. The surfer jams through the "back door" into what, in the late '60s and '70s, was often referred to as the "green room."

Backdooring a tube is an advanced move, not especially hard, but requiring nerves, a steady hand, and a deep store of tuberiding knowledge. Surfers will often backdoor a section by paddling to the far si...