Every small square in a grid of two rows and three columns has one diagonal drawn, all slanting the same way. How many triangles are there?

Each of the 6 small squares gives 2 halves, 12. Two pairs of diagonals line up into longer slanting lines, each across a 2 by 2 block of squares; each such line cuts its block into 2 big triangles, 4 more. Total $12+4=16$.