Excellent summary by Joe Carrick cut & paste from the "legacy forum":
Fill Patterns are simply text files that can be edited in a simple text editor like Notepad. Chief Architects supplies some standards and several custom patterns that are contained in the "Pattern" folder. Each Pattern is made up of a series of Lines. The format of a Pattern File is as follows: ;; PATTERN FILE NAME.PAT *1-PATTERN_NAME nAngle, xOrigin,yOrigin, xRepeatDelta,yOffset, [nLength,nSpace] .................................................. ...... .................................................. .. ................................................. nAngle = Angle of the Line (0 is horizontal - angles are measured clockwise) xOrigin,yOrigin = Start Coordinates of the Line xRepeatDelta = Offset of the Repeat Pattern (only valid when nLength & nSpace are present) yOffset = Spacing between Lines nLength = Length of a Line (if not provided the line is continuous) nSpace = negative value indicates length of a space. Example Pattern: *CEILING_GRID_24X48 0, 0,0, 0,24 0, 0,1, 0,24 90, 0,0, 0,48 90, 1,0, 0,48 This results in a pair of horizontal lines 1" apart repeated 24" o.c. and a pair of vertical lines 1" apart repeated 48" o.c. In most cases xRepeatDelta will be 0. If a specific length solid line and spacing is needed then [nLength,nSpace] should be specified as nLength,-nSpace such as 23,-1 to result in a line 23" long with a 1" space before the next solid line. Note that the above is very similar to the AutoCad format but Chief doesn't support a DOT in the Line definitions
