You wanted alternating spacings of 2'-0" and 2'-9". The offset between members of the same "family" of lines is constant, so one line cannot be spaced at 2'-0" and 2'-9", so you need two parallel line definitions, with a 2'-0" separation in their origin points, that are spaced at the total of the repeating pattern, which is 2'-0" + 2'-9" = 4'-9" (57 in the PAT file).
Each line in a hatch definition represents a "family" of lines. The angle of the line is specified in the first field, then the X and Y values of the origin point are specified in the next two fields. The X offset (offset along the length of the line, regardless of angle; only has meaning for a line that has a dash pattern specified) and the Y offset (offset between members of the family, perpendicular to the direct of the line, regardless of angle) are the fourth and fifth fields. Optional fields defining pen-down segments (dashes - positive values) and pen-up segments (gaps - negative values) can follow. For an RCP grid, the lines are continuous, so there are no optional dash fields in the file I attached.
The first line definition is
0, 0,0, 0,57
This creates a horizontal line (0-degree angle) with an origin at 0,0 that has an X-offset along the length of the line of 0 (no dashes, so any number would work) and a Y-offset perpendicular to the length of the line of 57 (4'-9"), so you would get a series of lines running horizontally, 57 units apart.
The second line definition is
0, 0,24, 0,57
This creates a second horizontal line with an origin at 0,24, putting it 24 units (2'-0") away from the first line. Like the first line, it is continuous, so the X-offset is meaningless and set to 0; the Y-offset is 57 (4'-9"), so this creates a second series of lines that are 57 units apart and 24 units (2'-0") from the previous line of the first line definition and 33 units (2'-9") from the following line of the first defintion line, creating the alternating 2-0" and 2'-9" spacing.
The third line defintion is
90, 0,0, 0,24
Since the spacing of the pattern in the other direction is a constant 2'-0", one line is all that is needed. The angle is 90, making it a vertical line, with an origin at 0,0. There is no X-offset along the length of the line, but there is a Y-offset perpendicular between lines of the same family of 24 units (2'-0").
David Koch
AutoCAD Architecture and Revit User
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