Think Tank was a staple of Tough Puzzles from the earliest days of the magazine, making its first appearance in the very first issue. At its heart it is a straightforward double acrostic, with a set of correctly solved clues - typically around 20 words of 7 to 12 letters each – leading to a quotation to be read across two rows. Rows 1 and 5 are normally the ones chosen, but this is occasionally varied. To make it worthy of the Tough label however, the clued words tend to test unusually esoteric pieces of general knowledge; to slightly ease this obscurity, the words used are broken down into two- and three-letter fragments, with all of the fragments presented together in alphabetical order.
Traditionally, three-letter fragments are used only where it is made necessary by an answer containing an odd number of letters, and this fact can often be used to provide the initial toe-hold into the puzzle.
For most of its lifespan (and in the sample provided), the puzzle was presented with vertical clues leading to a horizontally oriented quotation, but following a layout change in 2004, it is also often seen the other way round with horizontal clues and a vertical quotation.