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Hi,

When you add custom hatch pattern to AutoCAD with "Add pattern" from Hatch library, AutoCAD adds symbolic link (a kind of shortcut on PC) to the .PAT file you want to add to the "/Users/YOUR_USER_NAME/Library/Application Support/Autodesk/roaming/AutoCAD LT 2015 Standalone/R20.0/enu/Support/" folder.
So in order the hatch pattern be available you should not move it from the location from you added it.
The better solution is to add custom hatch patterns in another way:
- create special folder for your custom hatch patterns somewhere inside your Home folder, put them all ti this folder,
- add this folder to "Support files search path" in Application tab of AutoCAD preferences,
- restart AutoCAD. Now if you start HATCH command, open Hatch library and select "Custom" list - all hatch patterns should be ready for use.

This applies to hatch single hatch patterns definitions - one .PAT file = one hatch pattern.

If you have trouble with some specific .PAT files, you can attach one of them here - I'll look at it.

Maxim