Each image is a scrambled set of dual-image random-dot stereograms. Unlike
the single-image stereograms found in many popular 3-D art books, these are the
old-fashioned kind that use one image per eye.
To solve the clue, cut out the individual squares and find the pairs of
almost-matching squares (the random dots at the edge will be the same, but some
dots in the middle will differ). View each pair as a stereogram by laying the
two squares next to each other separated by an inch or two. You can use either
the wall-eyed or cross-eyed viewing technique (here are some
helpful hints). There
is a pair in the middle of the first page if you want to just try that one
instead of cutting out all the squares.
Each pair has a single bold letter standing out or receding (depending on
your viewing technique and which way you laid out the pair). The pairs on the
first page contain M, O, U, E, and two S's. The second page contains T, A, N,
and K. Answer: MOUSE'S TANK.
Clue author: Walter Smith