In the never ending quest to find more places and efficient ways to store stuff, we opted to build custom under bed storage. Nothing we can find in stores would properly utilize the space between the upright post and the wheel, and properly utilize the available height. Our solution, a custom built sliding drawer.

You'll need to adjust the dimensions to match what will fit under your own bed.

Our bed is 60" wide, and we intend to only have each drawer reach the half way point. The available width between the upright post and wheel is 30". While the available height appeared to be 6.5", the height at the middle of the bed is actually just under 6". There is a post (with foot) at the middle of the bed, that limits either our width or length. For our purposes we settled on a 30" wide x 29" long x 5 1/4" tall box. (The foot of one of the posts necessitated either reducing the width or the length).

Step 1: Gather the Materials and Tools

Parts

1/2" Plywood Sheet
1/4" Plywood Sheet
1" (or 3/4") Pocket Hole Screws. Qty 8.
5/8" Staples
2 1/2" Furniture Sliders (for Use on Carpet). Qty 4.
1 1/4" x 48" Wooden Dowel
#6 - 32 x 1 1/2" round head machine screws (with matching nuts). Qty 3
#6 Flat Washers. Qty 3.
5/8" staples

Tools

Screw driver
#6 Counter-sink bore drill bit
Drill
Table Saw
Radial Arm or Chop Saw (optional)
Pocket Hole Jig
Tape Measure
Pencil
Staple Gun
Clamps
Wrench or pliers
Sand paper or sanding block
Corner clamp (optional)

Step 2: Cut the Sides of the Box

You'll need to cut the sides of the box from the 1/2" plywood. Because of the joinery, deduct 1" from the length of the width you measured, for front and back panels. And deduct 1/4" from the height of all four side panels. I want a 30" wide by 29" long x 5 1/4" height box, so my cuts are as follows:

(2) 28"x5" panels (left and right sides)

(2) 30"x5" panels (front and back)

Step 3: Connect the Sides

For the joinery, I opted for pocket holes. You'll be drilling the pocket holes on the left/right side pieces. The left/right side pieces will nestle in between the front/back pieces (which is why we deducted the width of two boards from the cut dimension for the left/right side pieces).

Follow the directions for your pocket hole jig. For each left/right piece, you'll want to make two holes where it will connect to the front piece, and another two where it will connect to the back piece.

My jig recommends 3/4" pocket screws for the 1/2" plywood, but they are hard to find. I opted for 1" pocket hole screws, and slightly adjusted the jigs drill bit stop.

Once the pocket holes are drilled, you can attached the four sides (left/right/front/back) together. Utilize a corner clamp if you have one (I don't), to make sure the pieces are joined evenly at 90 degree angles. I utilize the table saw and guide to create a 90 degree edge to line the pieces up against while attaching the screws.

Step 4: Cut the Bottom Panel

I like to get the bottom panel cut after the sides of the box are attached (in case I screwed the math or cuts up slightly). Measure the width and length of your box to make sure you got what you were expecting (not accounting for the saw blade thickness can throw you off 1/16" to and 1/8"). My width and length matched the plan, 30"x29". Cut the appropriate sized panel from the 1/4" plywood.

(1) 30"x29" panel (bottom)

Step 5: Attach Bottom Panel

I opted to attach the bottom panel to the sides of the box with a staple gun. 5/8" staples did well, in my tests, for attaching 1/4" plywood to the edges of the 1/2" plywood.

Lay the box down. Line up the 1/4" plywood panel to all four sides of the box. You may benefit from laying some type of weight on the board. Using the staple gun, staple the bottom panel to the edges of the panel sides. I used 5 staples per edge.

Step 6: Cut the Wooden Dowel Handle to Length

I chose to make a handle. Partly to reduce costs, and partly to get a handle the same width (should make sliding it easier). I already had a 1 1/4" wooden dowel left over from an earlier project, and the diameter seems pretty good for a handle.

Measure, mark, and cut the wooden dowel to 30" (this should match the intended width of your box).

I used a radial arm saw to make the cut.

Step 7: Prepare the Handle for Installation

You'll need to drill countersunk holes for attaching the wooden dowel handle.

Clamp the dowel in place. My old versa bench work well for this. You'll want a consistent center line so all of your screws will attach to the box at the same angle. Mark off three evenly spaced points along the center line.

Using a 1/8" drill bit, pre-drill a pilot hole into the three marked points along the dowel.

Using a #6 countersink bit, drill into the three pilot holes. The bit should prevent you from drilling too far into the dowel. Note: The goal isn't to have the screw heads flush with the surface, you actually want them far enough through the dowel that they will securely attach to the front of the box.

Step 8: Attach the Handle

Utilizing some clamps, center and line the dowel up along the front of the box.

Because I opted for machine screws, you'll need to pre-drill into the front of the box. Using a 1/8" drill bit, line up with the existing holes in the dowel, but this time drill further so the bit gets through front panel's 1/2" plywood. Use a screw driver to attach the wooden dowel to the front panel face with three #6 round head machine screws. Put #6 washers on the alternate side of the screw (inside the box) and securely fasten with #6 nuts. Use a wrench or pair of pliers to turn the nut, while using the screw driver to keep the screw from spinning.

Step 9: Sand

Now is a good time to light sand all the side panels, and the edges where they meet. I utilized a sanding block. Brush off any remaining dust.

Step 10: Install the Furniture Sliders

Turn the box upside down. Line up furniture carper sliders in each of the four corners. One at a time, remove the adhesive backings and firmly press the slider into place for 30 to 60 seconds. If you are planning on storing something heavy, you may want to opt for an additional slider at the center.

Step 11: Slide Into Place

Make sure to load it up with your clothing (before your wife loads it up with hers), and slide it into place.

If your measurements (and assumptions) were accurate, it should slide easily under the bed and out of sight. Check the sliding and make sure the drawer isn't snagging anything on the sides or top of the bed frame.

Step 12: Optional - Stain or Paint the Box

It's been about 2 years, and I've made at least two more of these.

I made one much larger. I added dividers/supports, used 1/8" hard board for the bottom (with brad nails), stained it, and installed a nicer looking pull handle.