15. As shown below is a Go board, which consists of 19 horizontal and vertical lines each. Question: How many small squares, like the one in the right figure, are there on the Go board?



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100
15.【Solution】We first find a representative point in the small square on the right, for example, point $E$ at the bottom right corner as the representative point. Then place the small square on the Go board according to the problem, and carefully observe where point $E$ should be. Through observation, it is not difficult to find:
(1) Point $E$ can only be on the grid points of the square $A B C D$ (including the boundary) at the bottom right corner of the chessboard.
(2) Conversely, each grid point in the square $A B C D$ at the bottom right corner can serve as the point $E$ of a small square, and can only serve as the point $E$ of one small square.

In this way, the "number of small squares" is transformed into the "number of grid points in square $A B C D$". It is easy to see that the number of grid points in square $A B C D$ is $10 \times 10=100$.
Answer: There are 100 in total.