diff --git a/cameo/cameo.c b/cameo/cameo.c
index 2fef161..8d82073 100644
--- a/cameo/cameo.c
+++ b/cameo/cameo.c
@@ -13,11 +13,14 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#include <unistd.h>
 
 #include "path.h"
 #include "gnuplot.h"
 
 
+static int dog_bone = 0;
+
 
 static void process_path(struct path *path, int inside)
 {
@@ -26,9 +29,9 @@ static void process_path(struct path *path, int inside)
 
 	left = path_tool_is_left(path);
 	if (inside)
-		new = path_offset(path, !left, 0);
+		new = path_offset(path, !left, path->notch);
 	else
-		new = path_offset(path, left, 1);
+		new = path_offset(path, left, path->notch || dog_bone);
 	path_replace(path, new);
 }
 
@@ -61,8 +64,10 @@ static void process_paths(struct path *paths)
 
 static void usage(const char *name)
 {
-	fprintf(stderr, "usage: %s r_mm [in.gnuplot [out.gnuplot]]\n",
-	    name);
+	fprintf(stderr,
+"usage: %s [-d] r_mm [in.gnuplot [out.gnuplot]]\n\n"
+"  -d  put a dog-bone notch in each concave external corner\n"
+    , name);
 	exit(1);
 }
 
@@ -72,16 +77,26 @@ int main(int argc, char **argv)
 	char *in = NULL, *out = NULL;
 	double r;
 	struct path *paths;
+	int c;
 
-	switch (argc) {
-	case 4:
-		out = argv[3];
-		/* fall through */
+	while ((c = getopt(argc, argv, "d")) != EOF)
+		switch (c) {
+		case 'd':
+			dog_bone = 1;
+			break;
+		default:
+			usage(*argv);
+		}
+
+	switch (argc-optind) {
 	case 3:
-		in = argv[2];
+		out = argv[optind+2];
 		/* fall through */
 	case 2:
-		r = atof(argv[1]);
+		in = argv[optind+1];
+		/* fall through */
+	case 1:
+		r = atof(argv[optind]);
 		break;
 	default:
 		usage(*argv);
diff --git a/cameo/gnuplot.c b/cameo/gnuplot.c
index 239b803..566567b 100644
--- a/cameo/gnuplot.c
+++ b/cameo/gnuplot.c
@@ -26,7 +26,7 @@ struct path *gnuplot_read(const char *name, double r_tool_default)
 	char buf[1024];
 	double x, y, z, tmp;
 	double r_tool = r_tool_default;
-	int outside = 0;
+	int outside = 0, notch = 0;
 	int n;
 	struct path *paths = NULL, *path = NULL;
 	struct path **lnk = &paths;
@@ -43,6 +43,8 @@ struct path *gnuplot_read(const char *name, double r_tool_default)
 			r_tool = tmp;
 		if (!strcmp(buf, "#%outside\n"))
 			outside = 1;
+		if (!strcmp(buf, "#%notch\n"))
+			notch = 1;
 		if (*buf == '#')
 			continue;
 		n = sscanf(buf, "%lf %lf %lf\n", &x, &y, &z);
@@ -50,7 +52,7 @@ struct path *gnuplot_read(const char *name, double r_tool_default)
 		case -1:
 			path = NULL;
 			r_tool = r_tool_default;
-			outside = 0;
+			outside = notch = 0;
 			continue;
 		case 2:
 			z = 0;
@@ -66,6 +68,7 @@ struct path *gnuplot_read(const char *name, double r_tool_default)
 		if (!path) {
 			path = path_new(r_tool);
 			path->outside = outside;
+			path->notch = notch;
 			*lnk = path;
 			lnk = &path->next;
 		}
@@ -89,6 +92,8 @@ static int gnuplot_do_write(FILE *file, const struct path *paths)
 			return 0;
 		if (path->outside && fprintf(file, "#%%outside\n") < 0)
 			return 0;
+		if (path->notch && fprintf(file, "#%%notch\n") < 0)
+			return 0;
 		for (p = path->first; p; p = p->next)
 			if (fprintf(file, "%f %f %f\n", p->x, p->y, p->z) < 0)
 				return 0;
diff --git a/cameo/path.c b/cameo/path.c
index 6df4689..be3b37e 100644
--- a/cameo/path.c
+++ b/cameo/path.c
@@ -46,6 +46,7 @@ struct path *path_new(double r_tool)
 	path = alloc_type(struct path);
 	path->r_tool = r_tool;
 	path->outside = 0;
+	path->notch = 0;
 	path->first = path->last = NULL;
 	path->next = NULL;
 	return path;
@@ -58,6 +59,7 @@ static struct path *path_from(const struct path *old)
 
 	new = path_new(old->r_tool);
 	new->outside = old->outside;
+	new->notch = old->notch;
 	return new;
 }
 
diff --git a/cameo/path.h b/cameo/path.h
index 3f1b3ed..351ecef 100644
--- a/cameo/path.h
+++ b/cameo/path.h
@@ -24,6 +24,7 @@ struct path {
 	struct point *first, *last;
 	double r_tool;	/* mm */
 	int outside;	/* non-zero to mark path as an outside edge */
+	int notch;	/* non-zero to enable dog-boning for path */
 	struct path *next;
 };