This is an easy and hopefully fun to find gadget cache.
At GZ you will see a birdhouse.
Open the door on the birdhouse and you will see something that may be familiar to you.
Press the black button on the device and the log holder will drop down out of its holder (if it hangs give the house a tap), watch your feet.
After you have signed the log (bring your own pen or pencil) use the handle on the right side of the device to raise the log holder back into its hiding spot.
Please be gentle with this creation. No force needs to be used.