At a previous location (I forget exactly where) we had received a wheel-like cardboard device in a baggie labeled "You will use this later"
At clue site 16 (see Solution 15 for the exact location), we received the companion to the wheel, a cardboard navigation board that looked like this:
Go ahead and print them out - they are almost
full-size, and they're to scale, so they'll fit together and you can see
how the clue worked. You'll need a stickpin, and you should cut out the
white parts of the wheel.
Warning: this is a "you had to be there" clue so you will not actually be able to solve this one unless you go to the location.