The folks at Because We Can have made some seriously cool secret doors. There were a couple of helpful concepts I took away.
Context – a hidden door by itself stands out. Having other bookcases, or other similar design elements provide necessary camoflage. Location context can prove valuable, as well. If people don’t expect a room or a door there, it’s easier to conceal.
Proper hardware – there are hinges manufactured to have zero visibility from the outside. Special casters make sure your door doesn’t leave tell-tale marks on the floor. Strong wall anchors can minimize the profile of the rail for your sliding door.
There were resources offered for both d-i-y folks, and those who wanted to hire a pro. A very fun seminar.
Ah, the things you can learn at Maker Faire!