How can you put (without using glue or something like that) ten nails on the head of a standing nail? The final construction should be stable.

In the following way, you'll build a stable construction:

First, put down nine nails like in the picture below.


Then put one nail across.


Lift the whole construction gently, and put it on the head of the standing nail.

If you did it right, you'll see that this construction is pretty stable.