diff --git a/topola-egui/src/display.rs b/topola-egui/src/display.rs
index 9ebd53d..437ef1c 100644
--- a/topola-egui/src/display.rs
+++ b/topola-egui/src/display.rs
@@ -287,7 +287,9 @@ impl Display {
     ) {
         for layer in 0..*workspace.navmesher_board.board().layout().layer_count() {
             if workspace.appearance_panel.visible[layer] {
-                for navmesh in workspace.navmesher_board.navmesher().layers()[layer].navmeshes() {
+                for navmesh in
+                    workspace.navmesher_board.navmesher().layer_navmeshers()[layer].navmeshes()
+                {
                     for edge_geom in navmesh
                         .triangulation()
                         .rtreed_dcel()
diff --git a/topola/Cargo.toml b/topola/Cargo.toml
index 5dfe80f..690cf97 100644
--- a/topola/Cargo.toml
+++ b/topola/Cargo.toml
@@ -10,7 +10,7 @@ edition = "2024"
 
 [dependencies]
 bimap = "0.6"
-dearcut = { version = "0.3", features = ["undoredo"] }
+dearcut = { version = "0.3", features = ["serde", "undoredo"] }
 derive-getters.workspace = true
 derive_more.workspace = true
 rstar = "0.12"
diff --git a/topola/src/navmesher.rs b/topola/src/navmesher.rs
index 48aa325..af56580 100644
--- a/topola/src/navmesher.rs
+++ b/topola/src/navmesher.rs
@@ -2,7 +2,7 @@
 //
 // SPDX-License-Identifier: MIT OR Apache-2.0
 
-use dearcut::RecordingTriangulator;
+use dearcut::{RecordingTriangulator, VertexId};
 use derive_getters::Getters;
 use derive_more::Constructor;
 use serde::{Deserialize, Serialize};
@@ -16,12 +16,12 @@ use crate::{
 #[derive(
     Clone, Constructor, Copy, Debug, Deserialize, Eq, Ord, PartialEq, PartialOrd, Serialize,
 )]
-pub struct ObstacleId {
+pub struct MultiObstacleId {
     layer: usize,
     index: usize,
 }
 
-impl ObstacleId {
+impl MultiObstacleId {
     /// Layer of the obstacle.
     #[inline]
     pub fn layer(self) -> usize {
@@ -35,6 +35,20 @@ impl ObstacleId {
     }
 }
 
+#[derive(Clone, Constructor, Debug, Deserialize, Eq, Ord, PartialEq, PartialOrd, Serialize)]
+pub struct MultiVertexId {
+    layer: usize,
+    indices: Vec<VertexId>,
+}
+
+impl MultiVertexId {
+    /// Layer of the obstacle.
+    #[inline]
+    pub fn layer(self) -> usize {
+        self.layer
+    }
+}
+
 #[derive(Clone, Debug, Getters)]
 pub struct LayerNavmesher {
     boundary: Vec<Vector2<i64>>,
@@ -51,12 +65,15 @@ impl LayerNavmesher {
         }
     }
 
-    pub fn insert_obstacle(&mut self, polygon: impl IntoIterator<Item = Vector2<i64>>) -> usize {
+    pub fn insert_multiobstacle(
+        &mut self,
+        polygon: impl IntoIterator<Item = Vector2<i64>>,
+    ) -> usize {
         let polygon: Vec<Vector2<i64>> = polygon.into_iter().collect();
         let mut index = 0;
 
         for i in 0..self.navmeshes.len() {
-            index = self.navmeshes[i].insert_polygon_and_rebuild(
+            index = self.navmeshes[i].insert_obstacle_and_rebuild(
                 Self::inflate_polygon(polygon.clone(), self.inflation_factors[i])
                     .into_iter()
                     .map(Into::into),
@@ -98,11 +115,28 @@ impl LayerNavmesher {
             Vector2::new(rx as i64, ry as i64)
         })
     }
+
+    pub fn insert_free_multivertex_in_multiobstacle(
+        &mut self,
+        multiobstacle_index: usize,
+        position: Vector2<i64>,
+    ) -> Vec<VertexId> {
+        let mut vertices = Vec::new();
+
+        for navmesh in &mut self.navmeshes {
+            vertices.push(
+                navmesh
+                    .insert_free_vertex_in_obstacle(multiobstacle_index, [position.x, position.y]),
+            );
+        }
+
+        vertices
+    }
 }
 
 #[derive(Clone, Debug, Getters)]
 pub struct Navmesher {
-    layers: Vec<LayerNavmesher>,
+    layer_navmeshers: Vec<LayerNavmesher>,
 }
 
 impl Navmesher {
@@ -110,18 +144,33 @@ impl Navmesher {
         let boundary: Vec<Vector2<i64>> = boundary.into_iter().collect();
 
         Self {
-            layers: std::iter::repeat_with(|| LayerNavmesher::new(boundary.clone()))
+            layer_navmeshers: std::iter::repeat_with(|| LayerNavmesher::new(boundary.clone()))
                 .take(layer_count)
                 .collect(),
         }
     }
 
-    pub fn insert_obstacle(
+    pub fn insert_multiobstacle(
         &mut self,
         layer: usize,
-        polygon: impl IntoIterator<Item = Vector2<i64>>,
-    ) -> ObstacleId {
-        ObstacleId::new(layer, self.layers[layer].insert_obstacle(polygon))
+        multiobstacle: impl IntoIterator<Item = Vector2<i64>>,
+    ) -> MultiObstacleId {
+        MultiObstacleId::new(
+            layer,
+            self.layer_navmeshers[layer].insert_multiobstacle(multiobstacle),
+        )
+    }
+
+    pub fn insert_free_multivertex_in_multiobstacle(
+        &mut self,
+        multiobstacle_id: MultiObstacleId,
+        position: Vector2<i64>,
+    ) -> MultiVertexId {
+        MultiVertexId {
+            layer: multiobstacle_id.layer,
+            indices: self.layer_navmeshers[multiobstacle_id.layer]
+                .insert_free_multivertex_in_multiobstacle(multiobstacle_id.index, position),
+        }
     }
 }
 
@@ -130,9 +179,9 @@ pub struct NavmesherBoard {
     navmesher: Navmesher,
     board: Board,
 
-    joint_obstacles: Recorder<Vec<ObstacleId>>,
-    segment_obstacles: Recorder<Vec<ObstacleId>>,
-    polygon_obstacles: Recorder<Vec<ObstacleId>>,
+    joint_multiobstacles: Recorder<Vec<MultiObstacleId>>,
+    segment_multiobstacles: Recorder<Vec<MultiObstacleId>>,
+    polygon_multiobstacles: Recorder<Vec<MultiObstacleId>>,
 }
 
 impl NavmesherBoard {
@@ -148,23 +197,23 @@ impl NavmesherBoard {
             ),
             board,
 
-            joint_obstacles: Recorder::new(Vec::new()),
-            segment_obstacles: Recorder::new(Vec::new()),
-            polygon_obstacles: Recorder::new(Vec::new()),
+            joint_multiobstacles: Recorder::new(Vec::new()),
+            segment_multiobstacles: Recorder::new(Vec::new()),
+            polygon_multiobstacles: Recorder::new(Vec::new()),
         };
 
         for (i, joint) in this.board.layout().joints().collection() {
-            this.joint_obstacles.insert(
+            this.joint_multiobstacles.insert(
                 i,
                 this.navmesher
-                    .insert_obstacle(joint.layer, Self::joint_bounding_octagon(*joint)),
+                    .insert_multiobstacle(joint.layer, Self::joint_bounding_octagon(*joint)),
             );
         }
 
         for (i, segment) in this.board.layout().segments().collection() {
-            this.segment_obstacles.insert(
+            this.segment_multiobstacles.insert(
                 i,
-                this.navmesher.insert_obstacle(
+                this.navmesher.insert_multiobstacle(
                     segment.layer,
                     this.segment_bounding_rectangle(SegmentId::new(i), *segment),
                 ),
@@ -172,10 +221,10 @@ impl NavmesherBoard {
         }
 
         for (i, polygon) in this.board.layout().polygons().collection() {
-            this.polygon_obstacles.insert(
+            this.polygon_multiobstacles.insert(
                 i,
                 this.navmesher
-                    .insert_obstacle(polygon.layer, polygon.vertices.clone()),
+                    .insert_multiobstacle(polygon.layer, polygon.vertices.clone()),
             );
         }
 
@@ -184,10 +233,10 @@ impl NavmesherBoard {
 
     pub fn insert_joint(&mut self, joint: Joint) -> JointId {
         let joint_id = self.board.add_joint(joint);
-        self.joint_obstacles.insert(
+        self.joint_multiobstacles.insert(
             joint_id.id(),
             self.navmesher
-                .insert_obstacle(joint.layer, Self::joint_bounding_octagon(joint)),
+                .insert_multiobstacle(joint.layer, Self::joint_bounding_octagon(joint)),
         );
 
         joint_id
@@ -212,9 +261,9 @@ impl NavmesherBoard {
 
     pub fn insert_segment(&mut self, segment: Segment) -> SegmentId {
         let segment_id = self.board.add_segment(segment);
-        self.segment_obstacles.insert(
+        self.segment_multiobstacles.insert(
             segment_id.id(),
-            self.navmesher.insert_obstacle(
+            self.navmesher.insert_multiobstacle(
                 segment.layer,
                 self.segment_bounding_rectangle(segment_id, segment),
             ),
@@ -245,10 +294,10 @@ impl NavmesherBoard {
 
     pub fn insert_polygon(&mut self, polygon: Polygon) -> PolygonId {
         let polygon_id = self.board.add_polygon(polygon.clone());
-        self.polygon_obstacles.insert(
+        self.polygon_multiobstacles.insert(
             polygon_id.id(),
             self.navmesher
-                .insert_obstacle(polygon.layer, polygon.vertices),
+                .insert_multiobstacle(polygon.layer, polygon.vertices),
         );
 
         polygon_id