Ok this is my first Instructable and it's a bit on the large side so here goes.
Who doesn't love secret passages? I bought my first house last summer and over the cold winter ideas started forming in my mad scientist brain. As soon as it was warm enough to spend extended periods of time in the garage I got to work.

Step 1: Location

First up is the where. There is a closet under my stairs and about a one foot indentation along a nine foot wall. Seems like a pretty good spot! I pulled the door off and widened the opening to accommodate the bookshelf.

Step 2: Build the Bookcases

The first bookcase I made was a stationary one. I should have taken more pics of the process, especially the steps that apply to each section. The sides and shelves are 3/4 inch plywood. there are 2x4 braces on the bottom and 2x2 braces on the top. 1/4 plywood on the backs and tops. 1x6 pine to trim around the cases. 1 inch pipe and floor fittings for the hinge and casters for the door. When you figure out where you want the bookshelves, you need to leave a gap at the top and bottom. The top so the door won't scrape the ceiling, and the bottom for the casters. I routed a 3/4 inch channel 1/4 inch deep into each side for each shelf. Drill holes for 3 inch wood screws so that you don't split the wood and keep your square handy to make your shelves level. if you're sure they are level, nail the 1/4 plywood to the back for strength. I also screwed the stationary cases to the wall and each other.

Step 3: The Door

Most of the door bookcase construction is the same as the stationary ones. The big differences are 1) the door wont be resting directly on the floor and 2) it will be moving so i put an additional piece of 3/4 inch plywood on the back, bottom and top. For the bottom, attach a floor fitting to the corner that will pivot. Attach a string or wire to it and use as a compass to mark the curves that the casters will lay on. I attached the casters and fitting to the second piece of plywood with bolts and attached it to the other piece plywood, hiding the evidence. attach the pipe and another floor fitting and move the bookcase into place. Once in place, unscrew the pipe until the second fitting reaches the floor. Mark the holes position on the floor. Move the bookcase out of the way. Drill at the marked points and insert concrete anchors. Put the bookcase back in place and use lag bolts to anchor it to the floor. It will now hinge by screwing or unscrewing in the threads. Since it's only a quarter turn, there isn't a significant change in height. I repeated the pipe flange setup at the top to keep the case from wobbling. Just take careful measurements to put it in the same spot, or it will bind.

Step 4: Rest of the Shelves

Depending on your wall and shelf lengths, you may need more bookcases. I needed one more to bridge the gap between the two. Triple check your measurements. My last shelf ended up being a bit more narrow than the other two.

Step 5: Getting In

This room is the best space in case of storms, so I wanted a mechanical locking mechanism in case of power outages. To get in one one needs to have a magnetic item. When placed correctly, the magnet will stick. The panel warped slightly when cut and ended up keeping the latch tight until a little pressure is applied. Release both latches and voila hidden space. Springs in the back keep the panel from falling but still allow it to open. With the panel open, we see two cables. Pull one to lock and the other to unlock. This works really well right now, and if I want to go with a classic "book" opener it should be a pretty simple mod.

Step 6: The Latch

The latch is made of scrap plywood about 4" wide. I've got 2 bars that pivot on screws and are kept tight by rails. Another scrap of ply was used to sync the two bars together. I installed carabiners in line with the cables in case I want to lock any one out while I'm on the inside. The door is pretty secure when locked and takes a good shove to get it to move at all.

Step 7:

Stain to match existing wood and seal. Load with books and try to keep the secret. Or just show it off to all your friends. No one has figured it out yet without major clues. Now I just need to put together the mad science lab!