Letters With Transparent Overlay

A grid of random letters hides a clue, which is revealed by correctly positioning a transparent sheet over the top.

The grid below hides the clue "ON THE CLOCK". A transparent overlay with circles on it has to be correctly positioned on top of the grid to circle the correct letters to spell out the clue.

transparency letters 1 - grid of letters transparency letters 2 - overlay transparency letters 3 - clue revealed