Well this is a tutorial on how to make scan bars. This is an example of scan bars.
Regular:
[ Register or Signin to view external links. ]

Scan Bars:
[ Register or Signin to view external links. ]

Alright how to do it.
1.Make a new image (File-New)
2.Make the image 3 pixels by 3 pixels.
3.Zoom in until you can see it (Use the magnifying glass tool and look at the top and select fit screen)
4.Select the pencil and make three squares so it look like this:
[ Register or Signin to view external links. ]

5.Click edit-define pattern
6.Name it whatever you like
7.Open up whatever sig/image you want scan bars on
8.Make a new layer
9.Select the bucket/fill tool.
10.At the top left you should see this:
[ Register or Signin to view external links. ]

Select the option "pattern"
11.On the new layer fill it in.
12.Put it on overlay
13.You're done!