diff --git a/crates/model/src/lib.rs b/crates/model/src/lib.rs
index 5418553..d087a35 100644
--- a/crates/model/src/lib.rs
+++ b/crates/model/src/lib.rs
@@ -87,7 +87,7 @@ pub use steps::{
 };
 pub use tie::Tie;
 pub use units::UnitSystem;
-pub use virtual_faces::{FaceMerge, FaceSplit, Stitch};
+pub use virtual_faces::{Defeature, FaceMerge, FaceSplit, Stitch};
 
 /// The largest node or element label. Nastran's GRID and element ids stop at 99 999 999 (eight
 /// digits in a small field), the tightest of the three formats.
@@ -191,6 +191,9 @@ pub struct Model {
     /// Face splits along datum planes, in the order they apply (after the merges).
     #[serde(skip_serializing_if = "Vec::is_empty")]
     face_splits: Vec<FaceSplit>,
+    /// Features of the design taken out for meshing, in the order they were made.
+    #[serde(skip_serializing_if = "Vec::is_empty")]
+    defeatures: Vec<Defeature>,
 }
 
 /// A [`Model`] as stored, before it is checked.
@@ -253,6 +256,8 @@ struct ModelData {
     stitches: Vec<Stitch>,
     #[serde(default)]
     face_splits: Vec<FaceSplit>,
+    #[serde(default)]
+    defeatures: Vec<Defeature>,
 }
 
 impl TryFrom<ModelData> for Model {
@@ -355,6 +360,9 @@ impl TryFrom<ModelData> for Model {
         for v in d.face_splits {
             m.add_face_split(v)?;
         }
+        for v in d.defeatures {
+            m.set_defeature(v)?;
+        }
         Ok(m)
     }
 }
@@ -492,6 +500,7 @@ impl Model {
             face_merges: self.face_merges.clone(),
             stitches: self.stitches.clone(),
             face_splits: self.face_splits.clone(),
+            defeatures: self.defeatures.clone(),
         }
     }
 
@@ -542,7 +551,7 @@ impl Model {
     }
 
     /// Counts of each kind of definition, for summaries.
-    pub fn definition_counts(&self) -> [(&'static str, usize); 20] {
+    pub fn definition_counts(&self) -> [(&'static str, usize); 21] {
         [
             ("sets", self.sets.len()),
             ("materials", self.materials.len()),
@@ -564,6 +573,7 @@ impl Model {
             ("face_merges", self.face_merges.len()),
             ("stitches", self.stitches.len()),
             ("face_splits", self.face_splits.len()),
+            ("defeatures", self.defeatures.len()),
         ]
     }
 }
diff --git a/crates/model/src/virtual_faces.rs b/crates/model/src/virtual_faces.rs
index 151ca13..4205dc4 100644
--- a/crates/model/src/virtual_faces.rs
+++ b/crates/model/src/virtual_faces.rs
@@ -237,3 +237,56 @@ mod tests {
         assert_eq!(m.face_merges().len(), 2);
     }
 }
+
+/// Most defeatures a model holds.
+pub const MAX_DEFEATURES: usize = 1024;
+/// Most features one defeature names.
+pub const MAX_DEFEATURE_FEATURES: usize = 1024;
+
+/// Features of the design's timeline taken out for meshing (`geometry.defeature`): holes filled,
+/// fillets and chamfers back to their sharp edges, bosses removed, by feature id (`F<id>` in
+/// persistent names).
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct Defeature {
+    pub name: String,
+    pub features: Vec<u64>,
+}
+
+impl Model {
+    /// The defeatures, in the order they were made.
+    pub fn defeatures(&self) -> &[Defeature] {
+        &self.defeatures
+    }
+
+    /// Add a defeature, or replace the features of the one of that name (in its place).
+    pub fn set_defeature(&mut self, defeature: Defeature) -> Result<()> {
+        let name = defeature.name.clone();
+        check_name("defeature", &name)?;
+        let invalid = |m: String| context("defeature", &name, Error::Invalid(m));
+        if defeature.features.is_empty() || defeature.features.len() > MAX_DEFEATURE_FEATURES {
+            return Err(invalid(format!("1 to {MAX_DEFEATURE_FEATURES} features")));
+        }
+        let mut seen = std::collections::BTreeSet::new();
+        if let Some(id) = defeature.features.iter().find(|id| !seen.insert(**id)) {
+            return Err(invalid(format!("feature F{id} is listed twice")));
+        }
+        match self.defeatures.iter().position(|d| d.name == name) {
+            Some(i) => {
+                if let Some(d) = self.defeatures.get_mut(i) {
+                    *d = defeature;
+                }
+            }
+            None if self.defeatures.len() >= MAX_DEFEATURES => {
+                return Err(Error::Limit(format!("a model holds at most {MAX_DEFEATURES} defeatures")));
+            }
+            None => self.defeatures.push(defeature),
+        }
+        Ok(())
+    }
+
+    pub fn remove_defeature(&mut self, name: &str) -> Result<Defeature> {
+        let i = self.defeatures.iter().position(|d| d.name == name).ok_or_else(|| Error::NotFound(format!("defeature `{name}`")))?;
+        Ok(self.defeatures.remove(i))
+    }
+}