Answer:
18. The grid lines point to a Grid North, varying slightly from True North. This variation is smallest along the central meridian (vertical line) of the map, and greatest at the map edges. The difference between grid north and true north is very small and for most navigation purposes can almost always be ignored.
19. Most military maps will display the declination diagram in the lower margin. Some maps may not display the declination diagram and will only list the declination information as a note in the map margin. The G-M angle value is the size of the angle between grid north and magnetic north.
20. Must be oriented
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I believe its a hammer. Hopes this helps !