This is my Instructable on how to make "The Poor Man's Adjustable Bed Device" for a twin size bed. (Updated, see last step)

(Comments Appreciated!) :D

Materials you'll need:

1. Two plywood boards aprox. (35" x 31" x 0.5")
2. One plywood board aprox. (34" x 16.75" x 0.25")
3. Four strips of plywood aprox (34" x 1.5" x 0.25")
4. Thirty-six 0.45" finishing nails
5. Four hinges (with screws)
6. Six 0.5" screws with bolts
7. Six small plastic washers
8. White glue or wood glue
9. Two sheets of sandpaper (one medium one fine)
10. Paint, stain, transparent lacquer or varnish

Tools I used:

1. Jigsaw
2. Drill
3. Rotary Tool
4. Sander
5. Drill bits
6. Tape measure
7. Hammer
8. Screw driver

Step 1: Sanding

Using a sander, sand all the panels with the medium sandpaper then with the fine sandpaper.

Be sure to round off all the edges and corners. Since this will be used on a bed, you don't want any sharp edges or corners.

Note: The more time you spend on this step, the nicer the end-product will be. :)

Step 2: Install First Set of Hinges

Measure 7" and make a mark from the long edge of one of the boards and do the same on the opposite end.
Place one of the hinges on the edge of the board and trace around it with a pencil.
Do the same at the other end. (Note: The long edge represents the width of the bed it's to be used on. In this case it's a twin bed.)

Next, if you have a router or rotary tool, carve out the area where the hinge will go just enough to make it flush or almost flush. (This is purely asthetic, so you can omit this part).

Next, place the hinge in the carved-out hole and mark the center of each screw-hole with your pencil, then with a drill-bit, (thinner than the screws you'll be using), make starter-holes for the screws. Try not to drill all the way through to the other side of the board.

If your hinge screws are longer than the thickness of the board, (like mine were), cut them as necessary or find shorter screws.

Install the screws on both of the hinges. Close the hinges and place the other board on top and align all the edges as best as you can.

Next, while the board is on top of the other one, mark the placement of the hinges of the top board with your pencil.

Now, "open" the top board as if it were a book and as if the hinges were attached to it. Open the hinges and align them with the markings you made. Make sure the boards are as close as the hinges allow and then trace around each hinge with your pencil.

Next, perform the same procedure as above to make the hinges flush or just pre-drill the holes and install the screws.

Step 3: Install Second Set of Hinges

As before... on one of the boards, (choose the one that looks the nicest on the bottom side as this will be the main top board), measure 7" from the edge on each side and 13.5" from the edge, (where the two boards meet), and place a hinge and align it as square as possible. (I used my remaning board as a square to get them just right)

Once you have them just where you want them, trace around them with your pencil and mark the middle of each hole as well. Next, open the hinge so it's laying flat and also mark around the edges of the middle pin that holds the hinge together. Now, move the hinge aside and using the edge of the hinge as a ruler, draw two lines where the pin is located so that you end up with a small rectangle.

Next, using your rotary tool, carve-out the rectangle just enough to allow the hinge to sit flush (see second photo). Do the same with the other hinge.

Next, pre-drill the holes and install screws as shown.

Step 4: Install Stand

With your recently installed hinges in the closed position, place your last board on top of the hinges (as shown in first picture).

Align board with the other boards so that it's in the most square position possible.

Next, mark the edges of the board where the hinges will go.

Now, (as before), "open" the top board as if it were a book and algin the hinges to the markings you made and mark the center of each hole.

(Since this board is very thin, you will be using the 0.5" screws, washers and nuts here.)

Next, drill-out the holes using a drill-bit slightly larger than the thickness of the screws.

Now, attach the board to the hinges by placing the board between the hinges (very important) NOT as shown in the first picture. Insert each screw from the hinge side first, then the board. Add a plasic washers then the nuts.

If you did this correctly, when the hinge is in the "closed" position, the nuts should touch the other hinge. (See second photo)

Step 5: Install the Stops

Thoroughly sand all four strips of plywood untill smooth.

Take one strip and apply some glue on one side.

Next, place and center the strip almost to the edge of the opposite board, (the one without the stand & hinges), as shown in first picure.

Now, hammer-in one of the nails right in the middle of the strip. (try to not move the strip out of position when you do this. Also, be sure your nails are not too long. If they are, cut them so they don't come out the other side.)

Next, hammer-in a nail at about an inch from each end. Then do the middle between two nails and so forth until you have about 9 nails inserted. (see first photo)

Next, measure and mark from the edge of the first strip about 2.65". (make two marks near each edge of the board)

Apply glue to the next strip of plywood and apply the strip at the markings you just made. Insert nails as with the first strip.

Repeat until you have all four strips installed. (See second photo)

Step 6: Testing Postitions

If you've reached this step, you're almost done!

Now that you've installed the stops you should be able to position the main board in five different positions. (including completely horizontal)

(See photos)

Step 7: Finishing Touches

Now, all that remains is to paint, stain, lacquer or varnish your very own "Poor Man's Adjustable Bed" (Pat. Pend.) ;)

Finally, you can see it in use in the 2nd photo. :)

As you can see in this particular application, there is a thin memory foam matress on top of the main mattress. Obviously, for this device to work, you'll have to use a flexible mattress that's not too thick.

After observing the 2nd photo, I realized that maybe I could have made it a bit shorter. When I went to measure there were a lot of pillows in the way and didn't realize that the bed was that far away from the wall.

So, if you decide that this might be too long for your situation, you might want to adjust the measurements as needed. But it's nothing that can't be "fixed" buy moving the bed away from the wall as in this situation. :)

Update #1:

Although this project proved to be very useful, it became obvious that lifting the top board from the "Flat position" was sometimes a bit difficult so I decided to add a couple of handles to solve this problem. If you decide to also add the handles, be sure to drill the holes all the way through and use screws and nuts... you don´t want the handle to suddenly come off unexpectedly! (see added photos)

Update #2:

After using the device for some time, it became clear that it needed another modification. On the edge where the hinges are located it required some sort of tapering to minimize the small "step" that could be felt while in use. I purchased some Rubber Wall Base Molding at Home Depot and attached it to the end on both sides with rubber cement and thumbtacks and added some filling using one of those pool spaghetti floating devices cut in half lengthwise. (see added photos)