1 Use the rectangle marquee with Feather set to 0 px to select part of an image to use as a custom brush.
The brush shape can be up to 1024 pixels by 1024 pixels in size. To be most effective, the shape should appear on a solid white background. If you want to define brushes with soft edges, select brush shapes composed of pixels with gray values. (Colored brush shapes appear as gray values.)
2 Choose Define Brush from the Edit menu.
3 Name the brush and click OK.
4 In the New Brush dialog box, specify Spacing. (See Setting brush options.)
5 To make the brush placement more accurate, make sure that Anti-aliased is selected. (See Setting brush options.)