diff --git a/gridbeam.scad b/gridbeam.scad
old mode 100644
new mode 100755
index 8818611..19b056a
--- a/gridbeam.scad
+++ b/gridbeam.scad
@@ -1,105 +1,187 @@
-/*
- *  OpenSCAD GridBeam Library (www.openscad.org)
- *  Copyright (C) 2009 Timothy Schmidt
- *
- *  License: LGPL 2.1 or later
+/*********************************
+* OpenSCAD GridBeam Library      *
+* (c) Timothy Schmidt 2013       *
+* http://www.github.com/gridbeam *
+* License: LGPL 2.1 or later     *
+*********************************/
+
+/* Todo:
+ - implement "dxf" mode
 */
 
 // zBeam(segments) - create a vertical gridbeam strut 'segments' long
 // xBeam(segments) - create a horizontal gridbeam strut along the X axis
 // yBeam(segments) - create a horizontal gridbeam strut along the Y axis
+// zBolt(segments) - create a bolt 'segments' in length
+// xBolt(segments)
+// yBolt(segments)
 // topShelf(width, depth, corners) - create a shelf suitable for use in gridbeam structures width and depth in 'segments', corners == 1 notches corners
 // bottomShelf(width, depth, corners) - like topShelf, but aligns shelf to underside of beams
 // backBoard(width, height, corners) - create a backing board suitable for use in gridbeam structures width and height in 'segments', corners == 1 notches corners
 // frontBoard(width, height, corners) - like backBoard, but aligns board to front side of beams
 // translateBeam([x, y, z]) - translate gridbeam struts or shelves in X, Y, or Z axes in units 'segments'
 
-include <units.scad>
+// To render the DXF file from the command line:
+// openscad -x connector.dxf -D'mode="dxf"' connector.scad
+mode = "model";
+//mode = "dxf";
 
-$beam_width = inch * 1.5;
-$beam_hole_radius = inch * 5/16;
-$beam_is_hollow = 1;
-$beam_wall_thickness = inch * 1/8;
-$beam_shelf_thickness = inch * 1/4;
+include <MCAD/units.scad>
+
+beam_width = inch * 1.5;
+beam_hole_radius = inch * 5/16;
+beam_is_hollow = 1;
+beam_wall_thickness = inch * 1/8;
+beam_shelf_thickness = inch * 1/4;
 
 module zBeam(segments) {
+if (mode == "model") {
 	difference() {
-		cube([$beam_width, $beam_width, $beam_width * segments]);
+		cube([beam_width, beam_width, beam_width * segments]);
 		for(i = [0 : segments - 1]) {
-			translate([$beam_width / 2, $beam_width + 1, $beam_width * i + $beam_width / 2])
+			translate([beam_width / 2, beam_width + 1, beam_width * i + beam_width / 2])
 			rotate([90,0,0])
-			cylinder(r=$beam_hole_radius, h=$beam_width + 2);
+			cylinder(r=beam_hole_radius, h=beam_width + 2);
 
-			translate([-1, $beam_width / 2, $beam_width * i + $beam_width / 2])
+			translate([-1, beam_width / 2, beam_width * i + beam_width / 2])
 			rotate([0,90,0])
-			cylinder(r=$beam_hole_radius, h=$beam_width + 2);
+			cylinder(r=beam_hole_radius, h=beam_width + 2);
 		}
-	if ($beam_is_hollow == 1) {
-		translate([$beam_wall_thickness, $beam_wall_thickness, -1])
-		cube([$beam_width - $beam_wall_thickness * 2, $beam_width - $beam_wall_thickness * 2, $beam_width * segments + 2]);
-	}
+	if (beam_is_hollow == 1) {
+		translate([beam_wall_thickness, beam_wall_thickness, -1])
+		cube([beam_width - beam_wall_thickness * 2, beam_width - beam_wall_thickness * 2, beam_width * segments + 2]);
 	}
 }
+}
+
+if (mode == "dxf") {
+
+}
+}
 
 module xBeam(segments) {
-	translate([0,0,$beam_width])
+if (mode == "model") {
+	translate([0,0,beam_width])
 	rotate([0,90,0])
 	zBeam(segments);
 }
 
+if (mode == "dxf") {
+
+}
+}
+
 module yBeam(segments) {
-	translate([0,0,$beam_width])
+if (mode == "model") {
+	translate([0,0,beam_width])
 	rotate([-90,0,0])
 	zBeam(segments);
 }
 
+if (mode == "dxf") {
+
+}
+}
+
+module zBolt(segments) {
+if (mode == "model") {
+
+}
+
+if (mode == "dxf") {
+
+}
+}
+
+module xBolt(segments) {
+if (mode == "model") {
+}
+
+if (mode == "dxf") {
+
+}
+}
+
+module yBolt(segments) {
+if (mode == "model") {
+}
+
+if (mode == "dxf") {
+
+}
+}
+
 module translateBeam(v) {
 	for (i = [0 : $children - 1]) {
-		translate(v * $beam_width) child(i);
+		translate(v * beam_width) child(i);
 	}
 }
 
 module topShelf(width, depth, corners) {
+if (mode == "model") {
 	difference() {
-		cube([width * $beam_width, depth * $beam_width, $beam_shelf_thickness]);
+		cube([width * beam_width, depth * beam_width, beam_shelf_thickness]);
 
 		if (corners == 1) {
 		translate([-1,  -1,  -1])
-		cube([$beam_width + 2, $beam_width + 2, $beam_shelf_thickness + 2]);
-		translate([-1, (depth - 1) * $beam_width, -1])
-		cube([$beam_width + 2, $beam_width + 2, $beam_shelf_thickness + 2]);
-		translate([(width - 1) * $beam_width, -1, -1])
-		cube([$beam_width + 2, $beam_width + 2, $beam_shelf_thickness + 2]);
-		translate([(width - 1) * $beam_width, (depth - 1) * $beam_width, -1])
-		cube([$beam_width + 2, $beam_width + 2, $beam_shelf_thickness + 2]);
+		cube([beam_width + 2, beam_width + 2, beam_shelf_thickness + 2]);
+		translate([-1, (depth - 1) * beam_width, -1])
+		cube([beam_width + 2, beam_width + 2, beam_shelf_thickness + 2]);
+		translate([(width - 1) * beam_width, -1, -1])
+		cube([beam_width + 2, beam_width + 2, beam_shelf_thickness + 2]);
+		translate([(width - 1) * beam_width, (depth - 1) * beam_width, -1])
+		cube([beam_width + 2, beam_width + 2, beam_shelf_thickness + 2]);
 		}
 	}
 }
 
+if (mode == "dxf") {
+
+}
+}
+
 module bottomShelf(width, depth, corners) {
-	translate([0,0,-$beam_shelf_thickness])
+if (mode == "model") {
+	translate([0,0,-beam_shelf_thickness])
 	topShelf(width, depth, corners);
 }
 
+if (mode == "dxf") {
+
+}
+}
+
 module  backBoard(width, height, corners) {
-	translate([$beam_width, 0, 0])
+if (mode == "model") {
+	translate([beam_width, 0, 0])
 	difference() {
-		cube([$beam_shelf_thickness, width * $beam_width, height * $beam_width]);
+		cube([beam_shelf_thickness, width * beam_width, height * beam_width]);
 
 		if (corners == 1) {
 		translate([-1,  -1,  -1])
-		cube([$beam_shelf_thickness + 2, $beam_width + 2, $beam_width + 2]);
-		translate([-1, -1, (height - 1) * $beam_width])
-		cube([$beam_shelf_thickness + 2, $beam_width + 2, $beam_width + 2]);
-		translate([-1, (width - 1) * $beam_width, -1])
-		cube([$beam_shelf_thickness + 2, $beam_width + 2, $beam_width + 2]);
-		translate([-1, (width - 1) * $beam_width, (height - 1) * $beam_width])
-		cube([$beam_shelf_thickness + 2, $beam_width + 2, $beam_width + 2]);
+		cube([beam_shelf_thickness + 2, beam_width + 2, beam_width + 2]);
+		translate([-1, -1, (height - 1) * beam_width])
+		cube([beam_shelf_thickness + 2, beam_width + 2, beam_width + 2]);
+		translate([-1, (width - 1) * beam_width, -1])
+		cube([beam_shelf_thickness + 2, beam_width + 2, beam_width + 2]);
+		translate([-1, (width - 1) * beam_width, (height - 1) * beam_width])
+		cube([beam_shelf_thickness + 2, beam_width + 2, beam_width + 2]);
 		}
 	}
 }
 
+if (mode == "dxf") {
+
+}
+}
+
 module frontBoard(width, height, corners) {
-	translate([-$beam_width - $beam_shelf_thickness, 0, 0])
+if (mode == "model") {
+	translate([-beam_width - beam_shelf_thickness, 0, 0])
 	backBoard(width, height, corners);
-}
\ No newline at end of file
+}
+
+if (mode == "dxf") {
+
+}
+}