diff --git a/Cargo.toml b/Cargo.toml
index 83cc0dd..a44e5a8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -31,6 +31,7 @@ serde_json = "1.0.117"
 enum_dispatch = "0.3.12"
 itertools = "0.8.2"
 contracts = "0.6.3"
+bimap = "0.6.3"
 log = "0.4"
 
 [dependencies.serde]
diff --git a/src/autorouter/selection.rs b/src/autorouter/selection.rs
index 45abf73..ff49aef 100644
--- a/src/autorouter/selection.rs
+++ b/src/autorouter/selection.rs
@@ -67,8 +67,10 @@ impl Selection {
             NodeIndex::Compound(compound) => board.layout().zone(compound).layer(),
         };
 
-        if let (Some(pinname), Some(layername)) = (board.node_pinname(node), board.layername(layer))
-        {
+        if let (Some(pinname), Some(layername)) = (
+            board.node_pinname(node),
+            board.layout().rules().layer_layername(layer),
+        ) {
             Some(Selector {
                 pin: pinname.to_string(),
                 layer: layername.to_string(),
diff --git a/src/bin/topola-egui/overlay.rs b/src/bin/topola-egui/overlay.rs
index d56e14c..633ac21 100644
--- a/src/bin/topola-egui/overlay.rs
+++ b/src/bin/topola-egui/overlay.rs
@@ -6,11 +6,10 @@ use spade::InsertionError;
 
 use topola::{
     autorouter::{ratsnest::Ratsnest, selection::Selection},
-    board::Board,
+    board::{mesadata::MesadataTrait, Board},
     drawing::{
         graph::{GetLayer, MakePrimitive},
         primitive::MakePrimitiveShape,
-        rules::RulesTrait,
     },
     geometry::{
         compound::CompoundManagerTrait,
@@ -26,7 +25,7 @@ pub struct Overlay {
 }
 
 impl Overlay {
-    pub fn new(board: &Board<impl RulesTrait>) -> Result<Self, InsertionError> {
+    pub fn new(board: &Board<impl MesadataTrait>) -> Result<Self, InsertionError> {
         Ok(Self {
             ratsnest: Ratsnest::new(board.layout())?,
             selection: Selection::new(),
@@ -34,7 +33,7 @@ impl Overlay {
         })
     }
 
-    pub fn click(&mut self, board: &Board<impl RulesTrait>, at: Point) {
+    pub fn click(&mut self, board: &Board<impl MesadataTrait>, at: Point) {
         let geoms: Vec<_> = board
             .layout()
             .drawing()
@@ -65,7 +64,7 @@ impl Overlay {
 
     fn toggle_selection_if_contains_point(
         &mut self,
-        board: &Board<impl RulesTrait>,
+        board: &Board<impl MesadataTrait>,
         node: NodeIndex,
         p: Point,
     ) -> bool {
diff --git a/src/board/board.rs b/src/board/board.rs
index 87b095c..8570a85 100644
--- a/src/board/board.rs
+++ b/src/board/board.rs
@@ -24,8 +24,6 @@ use crate::{
 pub struct Board<M: MesadataTrait> {
     layout: Layout<M>,
     node_to_pinname: HashMap<NodeIndex, String>,
-    layer_to_layername: HashMap<u64, String>,
-    net_to_netname: HashMap<usize, String>,
     pinname_pair_to_band: HashMap<(String, String), BandIndex>,
 }
 
@@ -34,8 +32,6 @@ impl<M: MesadataTrait> Board<M> {
         Self {
             layout,
             node_to_pinname: HashMap::new(),
-            layer_to_layername: HashMap::new(),
-            net_to_netname: HashMap::new(),
             pinname_pair_to_band: HashMap::new(),
         }
     }
@@ -145,14 +141,6 @@ impl<M: MesadataTrait> Board<M> {
         result
     }
 
-    pub fn bename_layer(&mut self, layer: u64, layername: String) {
-        self.layer_to_layername.insert(layer, layername);
-    }
-
-    pub fn bename_net(&mut self, net: usize, netname: String) {
-        self.net_to_netname.insert(net, netname);
-    }
-
     pub fn zone_apex(&mut self, zone: GenericIndex<ZoneWeight>) -> FixedDotIndex {
         if let Some(apex) = self.layout.zone(zone).maybe_apex() {
             apex
@@ -176,14 +164,6 @@ impl<M: MesadataTrait> Board<M> {
         self.node_to_pinname.get(&node)
     }
 
-    pub fn layername(&self, layer: u64) -> Option<&String> {
-        self.layer_to_layername.get(&layer)
-    }
-
-    pub fn netname(&self, net: usize) -> Option<&String> {
-        self.net_to_netname.get(&net)
-    }
-
     pub fn band_between_pins(&self, pinname1: &str, pinname2: &str) -> Option<BandIndex> {
         if let Some(band) = self
             .pinname_pair_to_band
diff --git a/src/board/mesadata.rs b/src/board/mesadata.rs
index cdbf113..1e0b0f6 100644
--- a/src/board/mesadata.rs
+++ b/src/board/mesadata.rs
@@ -2,9 +2,11 @@ use crate::{drawing::rules::RulesTrait, layout::NodeIndex};
 
 // TODO: use this trait.
 pub trait MesadataTrait: RulesTrait {
-    /*fn node_pinname(&self, node: NodeIndex);
-    fn layer_layername(&self, layer: u64) -> &str;
-    fn layername_layer(&self, layername: &str) -> u64;
-    fn net_netname(&self, net: usize) -> &str;
-    fn netname_net(&self, netname: &str) -> usize;*/
+    fn bename_layer(&mut self, layer: u64, layername: String);
+    fn layer_layername(&self, layer: u64) -> Option<&str>;
+    fn layername_layer(&self, layername: &str) -> Option<u64>;
+
+    fn bename_net(&mut self, net: usize, netname: String);
+    fn net_netname(&self, net: usize) -> Option<&str>;
+    fn netname_net(&self, netname: &str) -> Option<usize>;
 }
diff --git a/src/drawing/drawing.rs b/src/drawing/drawing.rs
index 4eb49d8..badf80d 100644
--- a/src/drawing/drawing.rs
+++ b/src/drawing/drawing.rs
@@ -836,6 +836,12 @@ impl<CW: Copy, R: RulesTrait> Drawing<CW, R> {
         &self.rules
     }
 
+    #[debug_ensures(self.geometry_with_rtree.graph().node_count() == old(self.geometry_with_rtree.graph().node_count()))]
+    #[debug_ensures(self.geometry_with_rtree.graph().edge_count() == old(self.geometry_with_rtree.graph().edge_count()))]
+    pub fn rules_mut(&mut self) -> &mut R {
+        &mut self.rules
+    }
+
     pub fn guide(&self) -> Guide<CW, R> {
         Guide::new(self)
     }
diff --git a/src/dsn/design.rs b/src/dsn/design.rs
index 1610ed7..1a20f1d 100644
--- a/src/dsn/design.rs
+++ b/src/dsn/design.rs
@@ -4,7 +4,7 @@ use geo::{point, Point, Rotate, Translate};
 use thiserror::Error;
 
 use crate::{
-    board::Board,
+    board::{mesadata::MesadataTrait, Board},
     drawing::{dot::FixedDotWeight, seg::FixedSegWeight, Drawing},
     dsn::{
         de,
@@ -60,8 +60,7 @@ impl DsnDesign {
                         .layout()
                         .drawing()
                         .rules()
-                        .netname_to_net
-                        .get(&net_pin_assignments.name)
+                        .netname_net(&net_pin_assignments.name)
                         .unwrap();
 
                     // take the list of pins
@@ -70,7 +69,7 @@ impl DsnDesign {
                         .pins
                         .names
                         .iter()
-                        .map(|id| (id.clone(), *net))
+                        .map(move |pinname| (pinname.clone(), net))
                 })
                 // flatten the nested iters into a single stream of tuples
                 .flatten(),
@@ -88,8 +87,8 @@ impl DsnDesign {
                     .unwrap();
 
                 for pin in &image.pin_vec {
-                    let pin_name = format!("{}-{}", place.name, pin.id);
-                    let net = pin_nets.get(&pin_name).unwrap();
+                    let pinname = format!("{}-{}", place.name, pin.id);
+                    let net = pin_nets.get(&pinname).unwrap();
 
                     let padstack = &self
                         .pcb
@@ -117,7 +116,7 @@ impl DsnDesign {
                                     circle.diameter as f64 / 2.0,
                                     layer as u64,
                                     *net,
-                                    Some(pin_name.clone()),
+                                    Some(pinname.clone()),
                                 )
                             }
                             Shape::Rect(rect) => {
@@ -139,7 +138,7 @@ impl DsnDesign {
                                     rect.y2 as f64,
                                     layer as u64,
                                     *net,
-                                    Some(pin_name.clone()),
+                                    Some(pinname.clone()),
                                 )
                             }
                             Shape::Path(path) => {
@@ -159,7 +158,7 @@ impl DsnDesign {
                                     path.width as f64,
                                     layer as u64,
                                     *net,
-                                    Some(pin_name.clone()),
+                                    Some(pinname.clone()),
                                 )
                             }
                             Shape::Polygon(polygon) => {
@@ -179,7 +178,7 @@ impl DsnDesign {
                                     polygon.width as f64,
                                     layer as u64,
                                     *net,
-                                    Some(pin_name.clone()),
+                                    Some(pinname.clone()),
                                 )
                             }
                         };
@@ -189,12 +188,11 @@ impl DsnDesign {
         }
 
         for via in &self.pcb.wiring.via_vec {
-            let net = *board
+            let net = board
                 .layout()
                 .drawing()
                 .rules()
-                .netname_to_net
-                .get(&via.net)
+                .netname_net(&via.net)
                 .unwrap();
 
             // find the padstack referenced by this via placement
@@ -294,19 +292,17 @@ impl DsnDesign {
         }
 
         for wire in self.pcb.wiring.wire_vec.iter() {
-            let layer = *board
+            let layer = board
                 .layout()
                 .drawing()
                 .rules()
-                .layername_to_layer
-                .get(&wire.path.layer)
+                .layername_layer(&wire.path.layer)
                 .unwrap();
-            let net = *board
+            let net = board
                 .layout()
                 .drawing()
                 .rules()
-                .netname_to_net
-                .get(&wire.net)
+                .netname_net(&wire.net)
                 .unwrap();
 
             Self::add_path(
@@ -325,16 +321,22 @@ impl DsnDesign {
 
         // The clones here are bad, we'll have something better later on.
 
-        let layername_to_layer = &board.layout().drawing().rules().layername_to_layer.clone();
+        let layername_to_layer = &board.layout().drawing().rules().layer_layername.clone();
 
-        for (layername, layer) in layername_to_layer.iter() {
-            board.bename_layer(*layer, layername.to_string());
+        for (layer, layername) in layername_to_layer.iter() {
+            board
+                .layout_mut()
+                .rules_mut()
+                .bename_layer(*layer, layername.to_string());
         }
 
-        let netname_to_net = &board.layout().drawing().rules().netname_to_net.clone();
+        let netname_to_net = &board.layout().drawing().rules().net_netname.clone();
 
-        for (netname, net) in netname_to_net.iter() {
-            board.bename_net(*net, netname.to_string());
+        for (net, netname) in netname_to_net.iter() {
+            board
+                .layout_mut()
+                .rules_mut()
+                .bename_net(*net, netname.to_string());
         }
 
         board
@@ -343,15 +345,14 @@ impl DsnDesign {
     fn layer(
         board: &Board<DsnMesadata>,
         layer_vec: &Vec<Layer>,
-        layer_name: &str,
+        layername: &str,
         front: bool,
     ) -> usize {
-        let image_layer = *board
+        let image_layer = board
             .layout()
             .drawing()
             .rules()
-            .layername_to_layer
-            .get(layer_name)
+            .layername_layer(layername)
             .unwrap();
 
         if front {
diff --git a/src/dsn/mesadata.rs b/src/dsn/mesadata.rs
index 267d3b7..253b901 100644
--- a/src/dsn/mesadata.rs
+++ b/src/dsn/mesadata.rs
@@ -1,5 +1,7 @@
 use std::collections::HashMap;
 
+use bimap::BiHashMap;
+
 use crate::{
     board::mesadata::MesadataTrait,
     drawing::rules::{Conditions, RulesTrait},
@@ -27,42 +29,44 @@ pub struct DsnMesadata {
     // net class name -> rule
     class_rules: HashMap<String, DsnRule>,
 
-    // layernames -> layers for Layout
-    pub layername_to_layer: HashMap<String, u64>,
-    // netnames -> nets for Layout
-    pub netname_to_net: HashMap<String, usize>,
+    // layername <-> layer for Layout
+    pub layer_layername: BiHashMap<u64, String>,
+
+    // netname <-> net for Layout
+    pub net_netname: BiHashMap<usize, String>,
+
     // net -> netclass
-    net_to_netclass: HashMap<usize, String>,
+    net_netclass: HashMap<usize, String>,
 }
 
 impl DsnMesadata {
     pub fn from_pcb(pcb: &Pcb) -> Self {
-        let layer_ids = HashMap::from_iter(
+        let layer_layername = BiHashMap::from_iter(
             pcb.structure
                 .layer_vec
                 .iter()
-                .map(|layer| (layer.name.clone(), layer.property.index as u64)),
+                .map(|layer| (layer.property.index as u64, layer.name.clone())),
         );
 
         // keeping this as a separate iter pass because it might be moved into a different struct later?
-        let netname_to_net = HashMap::from_iter(
+        let net_netname = BiHashMap::from_iter(
             pcb.network
                 .class_vec
                 .iter()
                 .flat_map(|class| &class.net_vec)
                 .enumerate()
-                .map(|(id, net)| (net.clone(), id)),
+                .map(|(net, netname)| (net, netname.clone())),
         );
 
-        let mut net_id_classes = HashMap::new();
+        let mut net_netclass = HashMap::new();
         let class_rules = HashMap::from_iter(
             pcb.network
                 .class_vec
                 .iter()
                 .inspect(|class| {
-                    for net in &class.net_vec {
-                        let net_id = netname_to_net.get(net).unwrap();
-                        net_id_classes.insert(*net_id, class.name.clone());
+                    for netname in &class.net_vec {
+                        let net = net_netname.get_by_right(netname).unwrap();
+                        net_netclass.insert(*net, class.name.clone());
                     }
                 })
                 .map(|class| (class.name.clone(), DsnRule::from_dsn(&class.rule))),
@@ -71,14 +75,14 @@ impl DsnMesadata {
         Self {
             structure_rule: DsnRule::from_dsn(&pcb.structure.rule),
             class_rules,
-            layername_to_layer: layer_ids,
-            netname_to_net,
-            net_to_netclass: net_id_classes,
+            layer_layername,
+            net_netname,
+            net_netclass,
         }
     }
 
     pub fn get_rule(&self, net: usize) -> &DsnRule {
-        if let Some(netclass) = self.net_to_netclass.get(&net) {
+        if let Some(netclass) = self.net_netclass.get(&net) {
             self.class_rules
                 .get(netclass)
                 .unwrap_or(&self.structure_rule)
@@ -118,5 +122,27 @@ impl RulesTrait for DsnMesadata {
 }
 
 impl MesadataTrait for DsnMesadata {
-    //
+    fn bename_layer(&mut self, layer: u64, layername: String) {
+        self.layer_layername.insert(layer, layername);
+    }
+
+    fn layer_layername(&self, layer: u64) -> Option<&str> {
+        self.layer_layername.get_by_left(&layer).map(|s| s.as_str())
+    }
+
+    fn layername_layer(&self, layername: &str) -> Option<u64> {
+        self.layer_layername.get_by_right(layername).copied()
+    }
+
+    fn bename_net(&mut self, net: usize, netname: String) {
+        self.net_netname.insert(net, netname);
+    }
+
+    fn net_netname(&self, net: usize) -> Option<&str> {
+        self.net_netname.get_by_left(&net).map(|s| s.as_str())
+    }
+
+    fn netname_net(&self, netname: &str) -> Option<usize> {
+        self.net_netname.get_by_right(netname).copied()
+    }
 }
diff --git a/src/layout/layout.rs b/src/layout/layout.rs
index 0d02e69..3e6b840 100644
--- a/src/layout/layout.rs
+++ b/src/layout/layout.rs
@@ -211,6 +211,14 @@ impl<R: RulesTrait> Layout<R> {
         &self.drawing
     }
 
+    pub fn rules(&self) -> &R {
+        self.drawing.rules()
+    }
+
+    pub fn rules_mut(&mut self) -> &mut R {
+        self.drawing.rules_mut()
+    }
+
     pub fn zone(&self, index: GenericIndex<ZoneWeight>) -> Zone<R> {
         Zone::new(index, self)
     }
diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index 8073405..390ec50 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -78,8 +78,16 @@ pub fn assert_single_layer_groundless_autoroute(
             .layer();
 
         if let (Some(source_layername), Some(target_layername)) = (
-            autorouter.board().layername(source_layer),
-            autorouter.board().layername(target_layer),
+            autorouter
+                .board()
+                .layout()
+                .rules()
+                .layer_layername(source_layer),
+            autorouter
+                .board()
+                .layout()
+                .rules()
+                .layer_layername(target_layer),
         ) {
             dbg!(source_layername, target_layername);
             assert_eq!(source_layername, target_layername);
@@ -108,7 +116,7 @@ pub fn assert_single_layer_groundless_autoroute(
 
         let net = source_net.unwrap();
 
-        if let Some(netname) = autorouter.board().netname(net) {
+        if let Some(netname) = autorouter.board().layout().rules().net_netname(net) {
             // We don't route ground.
             if netname != "GND" {
                 dbg!(source_dot, target_dot);