Paint bookcases, desk extension piece, pegboard, and 1-by-2-inch boards if desired.
Using hacksaw or jigsaw, cut a piano hinge to height of bookcases. Cut the other hinge to length of a shelf; set aside for step 4.
To attach bookcases: Determine which bookcase will contain the desk and which will have the Plexiglas guards, as well as where the hinge should be placed to join them. Place the bookcases on their backs, side by side, shelves facing up. Place the hinge on the seam between them. Predrill holes through one side of hinge and along edge of one bookcase, making one hole near the top, one at the center and one near the bottom; insert 5/8-inch screws (or included screws) to secure. Repeat on edge of other bookcase. Predrill the remaining holes on both sides of hinge, and secure with screws. Stand joined bookcases upright.
To create desk extension: Using hacksaw or jigsaw, cut along the back edge of the center shelf to remove 1 inch from the width. Position the shelf in bookcase. Working from behind the bookcase, predrill holes where the shelf meets the back panel. Secure the shelf to the back panel with screws that are 3/4 inch longer than the thickness of the back panel. (You'll need a second person to secure the shelf against the back panel as you drill.) Place one side of the previously cut piano hinge along back edge of desk extension. Predrill holes through the hinge, making one hole at the right, one at the center, and one at the left. Secure with 5/8-inch screws (or the included screws). Predrill the remaining holes, and secure with screws. Align the other half of the piano hinge with the front edge of fixed center shelf. Repeat predrilling and drilling procedure to secure other side of hinge. Attach the lid stay or flap stay, following manufacturer's directions.
To secure Plexiglas guards: Create two rows of U-shaped molding that will run along sides and bottom of Plexiglas. Starting with the top shelf, place one shelf-long piece of molding about an inch from the front edge of the shelf. Using hammer, secure molding to shelf with 1-inch finish nails about every 6 inches, or where necessary. At each end, place one 2 1/2-inch piece of molding vertically. Secure to bookcase. In front of this existing piece, create another U-shape of molding, leaving just more than 1/4 inch of space in between for the guard. Repeat this procedure for the 3 middle shelves. For the bottom shelf, use the 8 1/2-inch molding as the vertical pieces. Once all the molding is in place, paint it to match the bookcase if desired, and let dry. Insert the Plexiglas guards between each pair of molding.
To attach the pegboard: Arrange 1-by-2-inch boards in a rectangle to match dimensions of pegboard. Set the pegboard on top of the rectangular frame, and secure it to boards by drilling 3/4-inch screws through the preexisting holes, in each corner and at top and bottom center. Fit the pegboard against panel behind the desk. Working from behind the bookcase, predrill holes where the top and bottom lengths of the pegboard frame will meet the back panel. Secure the frame with screws that are 3/4 inch longer than thickness of back panel. (You'll need a second person to secure the middle of the pegboard against the back panel as you drill.)
To install a draw-bolt latch or flush-mount lock outside the armoire: Close the bookcases. Predrill holes where the clasp will be affixed. Secure in place using the recommended screws and a drill.
To attach casters: Lay attached bookcases on the floor on their backs. Using a pencil, mark the bottom of each bookcase where the casters (4 per bookcase) will be placed. Place each caster about 2 inches from the corners. Predrill holes, then secure each caster with 3/4-inch screws (or the included screws). Stand the joined bookcases upright.
To affix desk side of bookcase to a wall (optional): Mark location of each L bracket on wall, making sure to mark the holes. The horizontal part of each L bracket will be attached along the case's top edge, 2 inches from the right and left sides; the vertical part of the bracket will be flush with the wall behind the bookcase. Insert wall anchors, and secure bracket to wall with screws. Position case so it is flush with wall or against baseboard. Predrill holes through bracket into case's top. Secure with 3/4-inch screws.
2 bookcases with adjustable shelves
Rectangular piece of wood (for desk extension): the same thickness as a shelf, 1/2 inch shorter than the length of a shelf, no more than 14 inches wide
Rectangular piece of pegboard (the length of a shelf with a height equal to the space between the desk shelf and the shelf above)
Four 1-by-2-inch boards (for pegboard frame): 2 cut to the height of the pegboard and 2 cut to its length minus 3 inches
Hacksaw or jigsaw with a metal blade (to cut piano hinge)
2 piano hinges (1 to attach bookcases and 1 to attach desk extension)
5/8-inch screws (for hinges, if screws aren't included)
Screws that are 3/4 inch longer than the thickness of desk-side bookcase's back panel (to secure existing desk shelf and pegboard frame)
Lid stay or flap stay
Glass-bead or other molding (to secure Plexiglas), cut into strips: 5 pieces the length of a shelf, 8 pieces 2 1/2 inches long, and 2 pieces 8 1/2 inches long
Hand miter saw (to cut molding)
3-D 1-inch finish nails (to secure molding for Plexiglas)
5 Plexiglas guards: 4 pieces cut 3 inches tall and to the length of a shelf and 1 piece cut 9 inches tall and to the length of a shelf
3/4-inch screws (to attach pegboard to frame; for casters, if screws aren't included; and for L brackets, if using)
Draw-bolt latch or flush-mount lock (for armoire latch)
8 casters (at least 1 inch)
Two 3-inch L brackets (to attach case to wall, optional)
Appropriate wall anchors and matching screws (for L brackets)
To complete this project, use two store-bought bookcases with adjustable shelves. (Avoid models more than 5 feet tall because they typically have a fixed center shelf.) You may want to cover the back of one -- one that will be the front of the armoire when closed -- with wallpaper or a higher-quality wood that's painted to match the project.
Maximize your work space by using a deeper bookcase for the side that will serve as the desk. (We used a 36-by-60-by-16-inch bookcase for the desk side and a 36-by-60-by-12-inch bookcase for the other side.)