The pentominoes

The pentominoes are flat shapes formed from five (Gr.pente = five) unit squares.
The squares must touch each other along an edge, but not merely at a corner.

The obtained shapes (12):

We can extend the set to the one-sided pentominoes (18).

There is a new form if the pentomino has no axis of symmetry.
With both sets we made the entire alphabet.
This next picture we got from Roel Huisman. He made it for our drawing competition.
Father Duck is filled with a set of one-sided pentominoes. Mother duck is made with a pentominoset and the small ducks are made together with a set.