diff --git a/src/layout.rs b/src/layout.rs
index 5bcbf06..d9ffcb1 100644
--- a/src/layout.rs
+++ b/src/layout.rs
@@ -44,6 +44,7 @@ use crate::shape::{Shape, ShapeTrait};
 use crate::wraparoundable::{GetWraparound, Wraparoundable, WraparoundableIndex};
 
 use self::bend::BendWeight;
+use self::seg::SegWeight;
 
 pub type RTreeWrapper = GeomWithData<Shape, GeometryIndex>;
 
@@ -77,7 +78,16 @@ pub struct AlreadyConnected(pub i64, pub GeometryIndex);
 pub struct Layout {
     rtree: RTree<RTreeWrapper>,
     connectivity: ConnectivityGraph,
-    geometry: Geometry<GeometryWeight, DotWeight, BendWeight, DotIndex, SegIndex, BendIndex>,
+    geometry: Geometry<
+        GeometryWeight,
+        DotWeight,
+        SegWeight,
+        BendWeight,
+        GeometryIndex,
+        DotIndex,
+        SegIndex,
+        BendIndex,
+    >,
 }
 
 #[debug_invariant(self.geometry.graph().node_count() == self.rtree.size())]
@@ -957,7 +967,16 @@ impl Layout {
     #[debug_ensures(self.geometry.graph().edge_count() == old(self.geometry.graph().edge_count()))]
     pub fn geometry(
         &self,
-    ) -> &Geometry<GeometryWeight, DotWeight, BendWeight, DotIndex, SegIndex, BendIndex> {
+    ) -> &Geometry<
+        GeometryWeight,
+        DotWeight,
+        SegWeight,
+        BendWeight,
+        GeometryIndex,
+        DotIndex,
+        SegIndex,
+        BendIndex,
+    > {
         &self.geometry
     }
 
diff --git a/src/layout/geometry.rs b/src/layout/geometry.rs
index 97d2f4a..8bff261 100644
--- a/src/layout/geometry.rs
+++ b/src/layout/geometry.rs
@@ -4,7 +4,7 @@ use enum_dispatch::enum_dispatch;
 use geo::Point;
 use petgraph::{
     stable_graph::{NodeIndex, StableDiGraph},
-    Direction::Incoming,
+    Direction::{Incoming, Outgoing},
 };
 
 use crate::{
@@ -26,7 +26,7 @@ use super::{
 };
 
 #[enum_dispatch]
-pub trait Retag {
+pub trait Retag<GeometryIndex> {
     fn retag(&self, index: NodeIndex<usize>) -> GeometryIndex;
 }
 
@@ -60,7 +60,7 @@ pub trait GetOffset {
 
 macro_rules! impl_weight {
     ($weight_struct:ident, $weight_variant:ident, $index_struct:ident) => {
-        impl Retag for $weight_struct {
+        impl Retag<GeometryIndex> for $weight_struct {
             fn retag(&self, index: NodeIndex<usize>) -> GeometryIndex {
                 GeometryIndex::$weight_variant($index_struct::new(index))
             }
@@ -106,7 +106,7 @@ macro_rules! impl_loose_weight {
     };
 }
 
-#[enum_dispatch(GetWidth, Retag)]
+#[enum_dispatch(GetWidth, Retag<GeometryIndex>)]
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub enum GeometryWeight {
     FixedDot(FixedDotWeight),
@@ -148,37 +148,45 @@ pub trait BendWeightTrait<GW>: GetOffset + GetWidth + Into<GW> + Copy {}
 
 #[derive(Debug)]
 pub struct Geometry<
-    GW: GetWidth + TryInto<DW> + TryInto<BW> + Copy,
-    DW: DotWeightTrait<GW>,
-    BW: BendWeightTrait<GW>,
-    DI: GetNodeIndex,
-    SI: GetNodeIndex,
-    BI: GetNodeIndex,
+    GW: GetWidth + TryInto<DW> + TryInto<SW> + TryInto<BW> + Retag<GI> + Copy,
+    DW: DotWeightTrait<GW> + Copy,
+    SW: SegWeightTrait<GW> + Copy,
+    BW: BendWeightTrait<GW> + Copy,
+    GI: GetNodeIndex + Copy,
+    DI: GetNodeIndex + Copy,
+    SI: GetNodeIndex + Copy,
+    BI: GetNodeIndex + Copy,
 > {
     pub graph: StableDiGraph<GW, GeometryLabel, usize>,
     weight_marker: PhantomData<GW>,
     dot_weight_marker: PhantomData<DW>,
+    seg_weight_marker: PhantomData<SW>,
     bend_weight_marker: PhantomData<BW>,
+    index_marker: PhantomData<GI>,
     dot_index_marker: PhantomData<DI>,
     seg_index_marker: PhantomData<SI>,
     bend_index_marker: PhantomData<BI>,
 }
 
 impl<
-        GW: GetWidth + TryInto<DW> + TryInto<BW> + Copy,
-        DW: DotWeightTrait<GW>,
-        BW: BendWeightTrait<GW>,
+        GW: GetWidth + TryInto<DW> + TryInto<SW> + TryInto<BW> + Retag<GI> + Copy,
+        DW: DotWeightTrait<GW> + Copy,
+        SW: SegWeightTrait<GW> + Copy,
+        BW: BendWeightTrait<GW> + Copy,
+        GI: GetNodeIndex + Copy,
         DI: GetNodeIndex + Copy,
         SI: GetNodeIndex + Copy,
         BI: GetNodeIndex + Copy,
-    > Geometry<GW, DW, BW, DI, SI, BI>
+    > Geometry<GW, DW, SW, BW, GI, DI, SI, BI>
 {
     pub fn new() -> Self {
         Self {
             graph: StableDiGraph::default(),
             weight_marker: PhantomData,
             dot_weight_marker: PhantomData,
+            seg_weight_marker: PhantomData,
             bend_weight_marker: PhantomData,
+            index_marker: PhantomData,
             dot_index_marker: PhantomData,
             seg_index_marker: PhantomData,
             bend_index_marker: PhantomData,
@@ -273,20 +281,6 @@ impl<
         self.core_weight(bend).width() / 2.0 + r
     }
 
-    fn inner(&self, index: NodeIndex<usize>) -> Option<NodeIndex<usize>> {
-        self.graph
-            .neighbors_directed(index, Incoming)
-            .filter(|node| {
-                matches!(
-                    self.graph
-                        .edge_weight(self.graph.find_edge(*node, index).unwrap())
-                        .unwrap(),
-                    GeometryLabel::Outer
-                )
-            })
-            .next()
-    }
-
     fn weight(&self, index: NodeIndex<usize>) -> GW {
         *self.graph.node_weight(index).unwrap()
     }
@@ -297,6 +291,12 @@ impl<
             .unwrap_or_else(|_| unreachable!())
     }
 
+    fn seg_weight(&self, seg: SI) -> SW {
+        self.weight(seg.node_index())
+            .try_into()
+            .unwrap_or_else(|_| unreachable!())
+    }
+
     fn bend_weight(&self, bend: BI) -> BW {
         self.weight(bend.node_index())
             .try_into()
@@ -342,6 +342,62 @@ impl<
             .unwrap()
     }
 
+    pub fn first_rail(&self, index: NodeIndex<usize>) -> Option<NodeIndex<usize>> {
+        self.graph
+            .neighbors_directed(index, Incoming)
+            .filter(|node| {
+                matches!(
+                    self.graph
+                        .edge_weight(self.graph.find_edge(*node, index).unwrap())
+                        .unwrap(),
+                    GeometryLabel::Core
+                )
+            })
+            .next()
+    }
+
+    pub fn core(&self, index: NodeIndex<usize>) -> Option<NodeIndex<usize>> {
+        self.graph
+            .neighbors(index)
+            .filter(|node| {
+                matches!(
+                    self.graph
+                        .edge_weight(self.graph.find_edge(index, *node).unwrap())
+                        .unwrap(),
+                    GeometryLabel::Core
+                )
+            })
+            .next()
+    }
+
+    pub fn inner(&self, index: NodeIndex<usize>) -> Option<NodeIndex<usize>> {
+        self.graph
+            .neighbors_directed(index, Incoming)
+            .filter(|node| {
+                matches!(
+                    self.graph
+                        .edge_weight(self.graph.find_edge(*node, index).unwrap())
+                        .unwrap(),
+                    GeometryLabel::Outer
+                )
+            })
+            .next()
+    }
+
+    pub fn outer(&self, index: NodeIndex<usize>) -> Option<NodeIndex<usize>> {
+        self.graph
+            .neighbors_directed(index, Outgoing)
+            .filter(|node| {
+                matches!(
+                    self.graph
+                        .edge_weight(self.graph.find_edge(index, *node).unwrap())
+                        .unwrap(),
+                    GeometryLabel::Outer
+                )
+            })
+            .next()
+    }
+
     pub fn graph(&self) -> &StableDiGraph<GW, GeometryLabel, usize> {
         &self.graph
     }
diff --git a/src/layout/seg.rs b/src/layout/seg.rs
index 4cf18d2..78a3f45 100644
--- a/src/layout/seg.rs
+++ b/src/layout/seg.rs
@@ -31,6 +31,39 @@ impl From<SegIndex> for GeometryIndex {
     }
 }
 
+#[enum_dispatch(GetWidth)]
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum SegWeight {
+    Fixed(FixedSegWeight),
+    LoneLoose(LoneLooseSegWeight),
+    SeqLoose(SeqLooseSegWeight),
+}
+
+impl From<SegWeight> for GeometryWeight {
+    fn from(seg: SegWeight) -> Self {
+        match seg {
+            SegWeight::Fixed(weight) => GeometryWeight::FixedSeg(weight),
+            SegWeight::LoneLoose(weight) => GeometryWeight::LoneLooseSeg(weight),
+            SegWeight::SeqLoose(weight) => GeometryWeight::SeqLooseSeg(weight),
+        }
+    }
+}
+
+impl TryFrom<GeometryWeight> for SegWeight {
+    type Error = (); // TODO.
+
+    fn try_from(weight: GeometryWeight) -> Result<SegWeight, ()> {
+        match weight {
+            GeometryWeight::FixedSeg(weight) => Ok(SegWeight::Fixed(weight)),
+            GeometryWeight::LoneLooseSeg(weight) => Ok(SegWeight::LoneLoose(weight)),
+            GeometryWeight::SeqLooseSeg(weight) => Ok(SegWeight::SeqLoose(weight)),
+            _ => unreachable!(),
+        }
+    }
+}
+
+impl SegWeightTrait<GeometryWeight> for SegWeight {}
+
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct FixedSegWeight {
     pub component: ComponentIndex,
diff --git a/src/primitive.rs b/src/primitive.rs
index beb5882..c68d8c6 100644
--- a/src/primitive.rs
+++ b/src/primitive.rs
@@ -87,26 +87,8 @@ pub trait GetFirstRail: GetLayout + GetNodeIndex {
     fn first_rail(&self) -> Option<LooseBendIndex> {
         self.layout()
             .geometry()
-            .graph()
-            .neighbors_directed(self.node_index(), Incoming)
-            .filter(|node| {
-                matches!(
-                    self.layout()
-                        .geometry()
-                        .graph()
-                        .edge_weight(
-                            self.layout()
-                                .geometry()
-                                .graph()
-                                .find_edge(*node, self.node_index())
-                                .unwrap()
-                        )
-                        .unwrap(),
-                    GeometryLabel::Core
-                )
-            })
+            .first_rail(self.node_index())
             .map(|node| LooseBendIndex::new(node))
-            .next()
     }
 }
 
@@ -114,26 +96,8 @@ pub trait GetCore: GetLayout + GetNodeIndex {
     fn core(&self) -> FixedDotIndex {
         self.layout()
             .geometry()
-            .graph()
-            .neighbors(self.node_index())
-            .filter(|node| {
-                matches!(
-                    self.layout()
-                        .geometry()
-                        .graph()
-                        .edge_weight(
-                            self.layout()
-                                .geometry()
-                                .graph()
-                                .find_edge(self.node_index(), *node)
-                                .unwrap()
-                        )
-                        .unwrap(),
-                    GeometryLabel::Core
-                )
-            })
+            .core(self.node_index())
             .map(|node| FixedDotIndex::new(node))
-            .next()
             .unwrap()
     }
 }
@@ -142,51 +106,15 @@ pub trait GetInnerOuter: GetLayout + GetNodeIndex {
     fn inner(&self) -> Option<LooseBendIndex> {
         self.layout()
             .geometry()
-            .graph()
-            .neighbors_directed(self.node_index(), Incoming)
-            .filter(|node| {
-                matches!(
-                    self.layout()
-                        .geometry()
-                        .graph()
-                        .edge_weight(
-                            self.layout()
-                                .geometry()
-                                .graph()
-                                .find_edge(*node, self.node_index())
-                                .unwrap()
-                        )
-                        .unwrap(),
-                    GeometryLabel::Outer
-                )
-            })
+            .inner(self.node_index())
             .map(|node| LooseBendIndex::new(node))
-            .next()
     }
 
     fn outer(&self) -> Option<LooseBendIndex> {
         self.layout()
             .geometry()
-            .graph()
-            .neighbors_directed(self.node_index(), Outgoing)
-            .filter(|node| {
-                matches!(
-                    self.layout()
-                        .geometry()
-                        .graph()
-                        .edge_weight(
-                            self.layout()
-                                .geometry()
-                                .graph()
-                                .find_edge(self.node_index(), *node)
-                                .unwrap()
-                        )
-                        .unwrap(),
-                    GeometryLabel::Outer
-                )
-            })
+            .outer(self.node_index())
             .map(|node| LooseBendIndex::new(node))
-            .next()
     }
 }