Index: trunk/src_plugins/rbs_routing/seq.c
===================================================================
--- trunk/src_plugins/rbs_routing/seq.c	(revision 38867)
+++ trunk/src_plugins/rbs_routing/seq.c	(revision 38868)
@@ -271,13 +271,36 @@
 	return res;
 }
 
+void rbsr_seq_step_back(rbsr_seq_t *rbsq)
+{
+	grbs_point_t *start;
 
+	if (rbsq->used <= 1)
+		return;
+
+	/* fallback for undoing the first seg., when rbsr_seq_redraw() won't fill
+	   it in: revert to start from the starting obj */
+	start = rbsq->path[0].pt;
+	rbsq->rlast_x = RBSR_G2R(start->x);
+	rbsq->rlast_y = RBSR_G2R(start->y);
+
+	/* remove the last segment from path and reset "consider" */
+	rbsq->used--;
+	rbsq->consider.dir = RBS_ADIR_invalid;
+	rbsr_seq_redraw(rbsq);
+
+	/* update routing-from coords for the tool code */
+	rbsq->last_x = rbsq->rlast_x;
+	rbsq->last_y = rbsq->rlast_y;
+}
+
 void rbsr_seq_end(rbsr_seq_t *rbsq)
 {
 	pcb_layer_t *ly = pcb_get_layer(rbsq->map.pcb->Data, rbsq->map.lid);
 
 	/* tune existing objects and install new objects */
-	rbsr_install_2net(ly, rbsq->tn);
+	if (rbsq->used > 0)
+		rbsr_install_2net(ly, rbsq->tn);
 
 	rbsr_map_uninit(&rbsq->map);
 }
Index: trunk/src_plugins/rbs_routing/seq.h
===================================================================
--- trunk/src_plugins/rbs_routing/seq.h	(revision 38867)
+++ trunk/src_plugins/rbs_routing/seq.h	(revision 38868)
@@ -39,4 +39,5 @@
 
 int rbsr_seq_consider(rbsr_seq_t *rbss, rnd_coord_t tx, rnd_coord_t ty, int *need_redraw_out);
 rbsr_seq_accept_t rbsr_seq_accept(rbsr_seq_t *rbss);
+void rbsr_seq_step_back(rbsr_seq_t *rbsq);
 
Index: trunk/src_plugins/rbs_routing/tool_seq.c
===================================================================
--- trunk/src_plugins/rbs_routing/tool_seq.c	(revision 38867)
+++ trunk/src_plugins/rbs_routing/tool_seq.c	(revision 38868)
@@ -115,9 +115,30 @@
 
 void pcb_tool_seq_escape(rnd_design_t *hl)
 {
-	rnd_tool_select_by_name(hl, "arrow");
+	if (pcb_crosshair.AttachedLine.State == PCB_CH_STATE_SECOND) {
+		seq.used = 0; /* do not create any object */
+		rbsr_seq_end(&seq);
+		pcb_crosshair.AttachedLine.State = PCB_CH_STATE_FIRST;
+	}
+	else
+		rnd_tool_select_by_name(hl, "arrow");
 }
 
+rnd_bool pcb_tool_seq_undo_act(rnd_design_t *hl)
+{
+	if (pcb_crosshair.AttachedLine.State != PCB_CH_STATE_SECOND)
+		return rnd_true;
+
+	if (seq.used <= 1)
+		pcb_tool_seq_escape(hl); /* undo starting click: return to STATE_FIRST */
+	else
+		rbsr_seq_step_back(&seq);
+
+	rnd_gui->invalidate_all(rnd_gui);
+	return rnd_false;
+}
+
+
 /* XPM */
 static const char *seq_icon[] = {
 /* columns rows colors chars-per-pixel */
@@ -160,8 +181,8 @@
 	NULL,
 	pcb_tool_seq_adjust_attached_objects,
 	pcb_tool_seq_draw_attached,
-	NULL, /* pcb_tool_seq_undo_act, */
-	NULL, /* pcb_tool_seq_redo_act, */
+	pcb_tool_seq_undo_act,
+	NULL, /*pcb_tool_seq_redo_act,*/
 	pcb_tool_seq_escape,
 
 	PCB_TLF_RAT