The Standard Six-Piece Burr:
This is the king of puzzles. Its origin is unknown, but it is ancient by puzzle standards, meaning the 18th century or possibly earlier. The problem is, it has now been established that there are well over 100,000 versions of the standard six-piece burr, so which one do we choose?
The puzzle consists of six notched square sticks, which form an interlocking structure of three mutually perpendicular pairs. When assembled, all the notches are hidden inside, so the puzzle has apparent total symmetry. In other words, if spun about, there is no way you can tell by the geometry if the same piece is still on top or a different one. This is basic to all totally symmetrical puzzles.
Since each stick interacts with four others, one or the other must be notched. All notices are in discrete units one-half the size of the sticks.
There are 25 such pieces - they are known as the set of notable pieces and are all in this model for you to download. Each piece has a number etched into the side and can be used in the following puzzle combinations amongst thousands of others. Search online for more puzzle but here is my favorite.
Burr #305 - 6, 12, 14, 21, 22 and 23