Burr Puzzle A block

The Burr puzzles usually take 6 pieces to form a Burr shape. On the easiest ones, the last piece, called a key, locks it all together. This is the Key piece, called A. The are five other pieces coming, three of one type, and two of another. This is the easiest of the many Burr puzzles.
This one puzzle is often called The Diabolical Structure . It really is not that tough. A good starter.