Biscuit Joinery !
Not the type you eat silly ! Biscuits are in theory 'flat dowels' made from compressed beech. They fit in a groove and expand when glue is applied, the provide a very strong joint ! This is because of their extra glue surface area and also the fact that they swell.
They are used in many areas of furniture - You can literally hold a piece of furniture together with these - some gurus and purists might raise an eyebrow at that though !
So heres how it's done:
Wow - that was fun. I hope thats explained how-to.
A few useful links: