This cache is made up of 2-3 layers(depending on what you call a layer). The first layer is about the size of two small Hide-a-Key's(or Key Holders). This is the "camo" layer. The second layer is about the size of two small Bison tubes. This is the part which gets a little tricky. You will have to open the second layer in a "clever" way. Please do not attempt break or force the second layer to open. Once you get the second layer open, you should be able to sign the log. Unfortunately, you will have to BYOP, but...well, you'll see.
UPDATE (as of 12/22/16): The cache now consists of only one layer and is no longer a field puzzle. Cache has been replaced in a similar hide.