This Is Tap (as officially spelled with a non-functional umlaut over the letter n — n-diaeresis — and a dotless letter i) is a 1984 mock musical documentary directed by Rob Reiner and starring members of the fictional heavy-metal/hard rock band Spinal Tap. The film satirizes the wild personal behavior and musical pretensions of hard-rock and heavy-metal musical bands, as well as the hagiographic tendencies of rock documentaries of the time.

Reiner and the three main stars are credited as the writers of the film, based on the fact that much of the dialogue was ad libbed by them. Several dozen hours of footage were filmed before Reiner edited it to the released film. A 4½ hour bootleg version of the film exists and has been traded among fans and collectors for years.spinaltapfan.com