HP LaserJet 4100 HP PCL/PJL reference (PCL 5 Printer Language) - Technical Ref - Page 220

A zero line type (0) draws only a dot at the X,Y coordinates for AA, AR, AT, CI, PA, PD, PR, and RT commands. Zero pen down values and zero length lines also produce dots. A dot is a one plotter unit long vector, drawn using the current line end and pen width. (Dots within lines are drawn at the correct angle, but zero length vectors are drawn along the user's current X-axis.) Negative line types (-1 - -8) are adaptive line types. The pattern length is automatically adjusted so that each line contains one or more complete patterns. Line patterns are composed of alternate pen down and pen up moves which are percentages of the pattern length (the first percentage is always pen down). 99 (LT99) restores the previous line type (and residue if it is a fixed-line type). Note If a solid line type is selected (LT;) when the LT99 command is issued, and the current pen position has not changed, the previously selected line type can be invoked using LT99. LT99 is ignored when a non-solid line type is in effect, or if the pen is in a different position than when the previous non-solid line ended. An example using this command is to print a line in a non-solid line type, followed by a rectangle in solid black; beginning at the end point of the previous line, use LT99 to print another line in the previous non-solid line type. Sending any of the following commands while plotting with a solid line type clears the previous line type and a subsequent (LT99) has no effect: Table 22-12 Commands that Affect LT99 Command Group AC,Anchor Corner The Line and Fill LA,Line Attributes Attributes Group LT,Line Type (except (LT) and (LT99) ) PW,Pen Width RF,Raster Fill Definition 22-24 The Line and Fill Attributes Group EN