Revit Fill Patterns (Hatch Patterns): Part 1

Revit Hatch Patterns: Part 1

Hatch patterns in Revit are referred to as 'Fill Patterns'.
When applied to a Revit material they can be either 'Surface Patterns' or 'Cut Patterns'.
Surface Patterns: Fill Patterns on an element in projection.
Cut Patterns: Fill Patterns on an element when cut.

Revit further divides them into 'Model' and 'Drafting'.
Model: Is always real world size (for instance 8"x4"x2.5"). Useful for measuring brick coursing.
Drafting: Is always a printed size (for instance measured off the sheet as 1/16"). Useful for representing diagonal masonry hatch no matter the scale.

Fill Patterns start life as a .pat file. The same file used in AutoCAD and other programs for hatches.
Here's a site with some free .pat files. As an example, you could download the Brickpat.zip file. This contains a bunch of sample brick hatches in .pat form. Take a look at the thirdrun.pat. These .pat files can be opened and edited in Notepad. Here's an AutoCAD dwg file made by Chirag Mistry which explains how to write and edit a .pat file for Revit. Most .pat files are 'Drafting' patterns according to Revit. In order to make them 'Model' patterns you need to add ";%TYPE=MODEL" to the second line of the pat file (without the quotations). You can do that to the thirdrun.pat file.

Once your .pat file is ready you can import it into Revit. This can be done under Manage-Additional Settings-Fill Patterns. You can then choose 'Drafting' or 'Model'.

Here are the steps for importing a .pat file:
Model
New
Custom
Import
Choose the .pat file. (thirdrun.pat)
Scale (this can only be changed on import)

You can also make simple crosshatch patterns within Revit (no need for a .pat file) . Just follow these steps:

Manage-Additional Settings-Fill Patterns. You can then choose 'Drafting' or 'Model'. 
Drafting or Model
New
Simple
Name
Line Angle
Line Spacing
Parallel Lines or Crosshatch

These Fill Patterns can now be applied to Filled Regions and Revit Materials.

Please read this AUGI thread for additional reference:
http://forums.augi.com/showthread.php?t=57164