I designed a few corner shelves that I thought would stand out. The first was circular, the second was a cube and the third was a diamond. Only one of them worked and I built it this week.

This is my first attempt at an instructable so I thought I'd start with something simple. I thought that 4 bits of wood would be easy to explain. And it is. It's the painting that proved a bit tricky. I designed this in sketchup (hence the very accurate measurements) so I was able to take the measurements straight off of my computer and still I managed to get it wrong....3 times!!

If, unlike me, you pay close attention to the measurements this is an easy and enjoyable build with an effective illusion at the end.

I have also made a companion video that can be used at any point to help you understand the more tricky elements of this build.

Required Tools

A means of cutting wood in a straight line i.e. a Jigsaw, Plunge/Circular Saw, Table Saw or a Panel Saw if you're feeling confident.

Measuring Tape

Steel Ruler

Sharp craft knife

Masking tape

A paint brush

White and Black Paint

A Drill

A Counter sink drill bit

A screw bit

A handful of screws (I used 15 4x40 screws)

Wood glue

Filler and spatula/scraper

Sandpaper (I used 180 and 240 grit)

Step 1: Cutting

I used 18mm Birch Ply wood that I had left over from another job. This particular bit of wood had been used on the floor and had screw holes, cracks and foot prints all over it. I sanded off the foot prints until it was clean, I filled and sanded every hole and did my best to avoid any cracks.

Cutting List (18mm Ply)

438mm x 438mm (Top)
438mm x 438mm (Bottom)
438mm x 420mm (Left)
420mm x 420mm (Right)

The inside measurement of the box is 420mm, or 42cm. 42 is the answer to life, the universe and everything and you may find that number crops up a lot in my designs. 438mm is (obviously) just an added 18mm on top for the depth of a piece of ply that will be glued and screwed into it.

Once you have cut each board to size you'll need to paint them white. The 438mm x 420mm and 420mm x 420mm boards only need to be painted on one side. Both 438mm x 438mm boards need to be painted on both sides.

I applied two coats of paint throughout this project.

Step 2: Masking Out

Now here's the tricky bit. I've done my best to make the pictures as easy to understand as possible.

Picture 1

This is the 420mm x 420mm (Right).

Mark 18mm in from the edge and mask off with tape.

Picture 2

This is the 438mm x 420mm (Left). For ease of explanation, lay the board down with the 438mm measurement going from left to right and the 420mm measurement going top to bottom.

Mask out 18mm around the bottom, left and top edges of the board and then mask 36mm down the right edge.

Measure in from the 36mm mark 109.4mm (I'm aware of the crazy accurate measurements, but I wanted mine to be perfect and yours).

The stripe that goes from top to bottom measures 25.5mm wide.

This should leave 249.1mm on the left side of the stripe.

Picture 3

This is 438mm x 438mm (Bottom).

Mask in 18mm on the bottom and left edges of the board and 36mm on the top and right edges.

Starting with the bottom left corner, (heading up and right) mark in pencil 12.7mm in from the corner of the tape.

These two marks should be 18mm apart. The stripe that runs from this corner fans out to 25.5mm wide.

From the top left corner of the tape, mark in 119.6mm.

Then mark 25.5mm for the stripe.

This should leave you with 238.9mm to the left of the stripe.

Picture 4

This is 438mm x 438mm (Top)

This is a mirrored image of Picture 3 (Bottom).

Mask in 18mm on the bottom and right edges of the board and 36mm on the top and left edges.

Starting with the bottom right corner, (heading up and left) mark in pencil 12.7mm in from the corner of the tape.

These two marks should be 18mm apart. The stripe that runs from this corner fans out to 25.5mm wide.

From the top right corner of the tape, mark in 119.6mm.

Then mark 25.5mm for the stripe.

This should leave you with 238.9mm to the right of the stripe.

Not Pictured

After you have masked everything off you need to flip both 438mm x 438mm (Top and Bottom) boards over and mask off 18mm around the edges.

Step 3: Painting

Once all the masking is completed it's worth holding each board up in position to see that the masking all lines up. This was the point that I realised I had masked off incorrectly, so it's worth checking.

Paint black on the outside of your masking on each board. Understanding the orientation of each board will help you figure out which edges need to be painted.

420mm x 420mm (Right) needs one edge painted black.

438mm x 420mm (Left) needs painting black on the opposite end from the extra 18mm overlap.

Both 438mm x 438mm boards need to be painted black on the two facing edges opposite to the 36mm borders.

Once the paint has dried it's worth scoring the edge of the masking tape with a sharp knife to prevent any tear away when peeling the masking tape off.

Now the satisfying job of peeling your masking tape off to reveal the finished faces.

Leave the masking tape on the flip side of the 438mm x 438mm boards for a later step.

Touch up any stray bits of black with some white paint.

Step 4: Assembly

Now it's time for assembly.

Counter sink and screw the 420mm x 420mm (Right) into the 438mm x 420mm (Left) making sure that the 36mm border is half covered up by the righthand board.

Now counter sink, glue and screw the 438mm x 438mm (Top and Bottom) boards making sure that they are orientated correctly. The 36mm borders should help with this.

Once it is assembled you can filler the counter sunk screws on the top and bottom of the piece. Sand flush and paint black.

Score the masking tape again with a sharp knife and ruler and then peel off.

Finish with some clear lacquer.

And now you have a 3D Corner Shelf.