The top slides out.

The wedges on all the four sides don't connect in a cross inside. That is, they're not connected to the wedges on the opposite sides. Instead, two of the wedges connect to the two on either side of them.

In the picture, the wedge on the right connects to the unseen wedge on the right at the back. And the wedge on the left connects to the unseen wedge on the left at the back of the block.

The lid would have similar grooves.

I'd be tempted to say that one of the dovetails isn't real (e.g. painted on) so the blocks can move freely.

It's also possible that the two dovetails we see are connected to eachother, and there aren't dovetails on the other two sides.

the grooves are actually parallel to each other and at a 45 degree angle from the cube faces. This way the top half of the cube can be pushed straight backwards relative to the orientation of the cube in the picture, along a line connecting the front corner and the back corner.

wow this is one of the worst "illusions" i have ever seen.

Well, interesting idea, but if abhijit is right, then it is not an illusion - just a trick (however, i'm not gonna use the websters on this :) Nice idea, anyway

'intelligence', it's a trick on the mental model that humans create when they see something and attempt to evaluate it. Because we see two flat faces each with a jig-saw piece-style groove on it, we assume we understand (or rather we attempt to complete what we can't see) the innards of the shape to be a cross piece locking the two together.

What if the bottom is made out of soft sponge?

what if the dovetail is circular? derrrrrrr!

So what's the answer? Isn't it possible that the top swings out along a semicircular dovetail-rail?

This is real, dovetails on all 4 sides. The reason it works is that the skewed crossection of a small dovetail is a bigger dovetail. So it looks normal on the flat plane of the surface when assembled. By comparison a circle would look like an oval when sliced in the same manner.

I was tempted to rotate the pieces. Without knowing what's on the other side, it could have easily twisted apart.

It is one piece of wood! It never came apart.

the bottom half is cut diagnolly so that u can slide both sides of the bottom out.
im not very good at explaning, so dont worry if u dont understand me ;P

oh i love dovetail puzzles!

those ones are super simple....i have a few that i've never managed to open, but i do know that soem of them have magnets that you have to disconnect in just the right way....

maybe i'll send you pictures!

I get it though

good trick to the eyes

another way could be if the two wedges were either end of an arc, then you would simply have to swivel the top off

it slides out diagnolly took me 2 seconds to figure out

Why debate the solution is there, it slides as the pic says.

I am 12 and I know it!