You can save time hatching a small area in a complex drawing by defining a set of objects in the drawing to be used in determining the hatch boundary.
By default, HATCH defines the boundary by analyzing all closed objects in the drawing. Analysis of all objects fully or partially visible on the screen as boundaries can be time consuming in a complex drawing. To hatch a small area of a complex drawing, you can define a set of objects in the drawing called a boundary set. HATCH does not analyze objects that are not included in the boundary set.
For clarity, first zoom into the area you want to hatch.
The View Selections option in the Hatch and Gradient dialog box, highlights the objects in the drawing that define the boundary.