The steps below can be used in ArcView GIS 3.x to clip a grid with another theme's extent. The theme being clipped can be from any data source, such as anything on a map. ArcView Spatial Analyst extension is required.
In a view, add or create the desired theme and the desired grid.
From the Analysis menu, select Properties.
From the Analysis Extent dropdown list, select the theme that you added or created in step 1.
Click OK to exit the Properties dialog box.
Return to the Analysis menu and select Map Calculator.
Double-click on the grid used in step 1 to add it to the expression box.
Click Evaluate. The results will be added to the Table of Contents.
If you approve of the results, make the grid permanent by selecting Save Data Set.