diff --git a/README.md b/README.md
index ab063e3f5..316e095dd 100644
--- a/README.md
+++ b/README.md
@@ -62,10 +62,7 @@ pub extern "C" fn model(args: &HashMap<String, String>) -> fj::Shape {
         b: inner_edge.into(),
     };
 
-    let spacer = fj::Sweep {
-        shape: footprint.into(),
-        length: height,
-    };
+    let spacer = fj::Sweep::from_shape_and_length(footprint.into(), height);
 
     spacer.into()
 }
diff --git a/fj/src/shape_3d.rs b/fj/src/shape_3d.rs
index c884b7db3..4d7d96f9e 100644
--- a/fj/src/shape_3d.rs
+++ b/fj/src/shape_3d.rs
@@ -62,15 +62,29 @@ impl From<Transform> for Shape3d {
 #[repr(C)]
 pub struct Sweep {
     /// The 2-dimensional shape being swept
-    pub shape: Shape2d,
+    shape: Shape2d,
 
     /// The length of the sweep
-    pub length: f64,
+    length: f64,
+}
+
+impl Sweep {
+    pub fn from_shape_and_length(shape: Shape2d, length: f64) -> Self {
+        Self { shape, length }
+    }
+
+    pub fn shape(&self) -> &Shape2d {
+        &self.shape
+    }
+
+    pub fn length(&self) -> f64 {
+        self.length
+    }
 }
 
 impl From<Sweep> for Shape {
     fn from(shape: Sweep) -> Self {
-        Self::Shape3d(Shape3d::Sweep(shape))
+        Self::Shape3d(shape.into())
     }
 }
 
diff --git a/fj/src/syntax.rs b/fj/src/syntax.rs
index 31e57d8a5..b62a693cf 100644
--- a/fj/src/syntax.rs
+++ b/fj/src/syntax.rs
@@ -44,7 +44,7 @@ where
 {
     fn sweep(&self, length: f64) -> crate::Sweep {
         let shape = self.clone().into();
-        crate::Sweep { shape, length }
+        crate::Sweep::from_shape_and_length(shape, length)
     }
 }
 
diff --git a/models/cuboid/src/lib.rs b/models/cuboid/src/lib.rs
index e7146d90e..73046c55b 100644
--- a/models/cuboid/src/lib.rs
+++ b/models/cuboid/src/lib.rs
@@ -14,10 +14,7 @@ pub extern "C" fn model(args: &HashMap<String, String>) -> fj::Shape {
         [-x / 2.,  y / 2.],
     ]);
 
-    let cuboid = fj::Sweep {
-        shape: rectangle.into(),
-        length: z,
-    };
+    let cuboid = fj::Sweep::from_shape_and_length(rectangle.into(), z);
 
     cuboid.into()
 }
diff --git a/models/spacer/src/lib.rs b/models/spacer/src/lib.rs
index 3a84e8e98..5ab897c52 100644
--- a/models/spacer/src/lib.rs
+++ b/models/spacer/src/lib.rs
@@ -26,10 +26,7 @@ pub extern "C" fn model(args: &HashMap<String, String>) -> fj::Shape {
         b: inner_edge.into(),
     };
 
-    let spacer = fj::Sweep {
-        shape: footprint.into(),
-        length: height,
-    };
+    let spacer = fj::Sweep::from_shape_and_length(footprint.into(), height);
 
     spacer.into()
 }
diff --git a/models/star/src/lib.rs b/models/star/src/lib.rs
index 8bfb958ad..58d9ec3a3 100644
--- a/models/star/src/lib.rs
+++ b/models/star/src/lib.rs
@@ -58,10 +58,7 @@ pub extern "C" fn model(args: &HashMap<String, String>) -> fj::Shape {
         b: inner.into(),
     };
 
-    let star = fj::Sweep {
-        shape: footprint.into(),
-        length: h,
-    };
+    let star = fj::Sweep::from_shape_and_length(footprint.into(), h);
 
     star.into()
 }
diff --git a/src/kernel/shapes/sweep.rs b/src/kernel/shapes/sweep.rs
index 9b2c06e01..d9834a208 100644
--- a/src/kernel/shapes/sweep.rs
+++ b/src/kernel/shapes/sweep.rs
@@ -9,15 +9,15 @@ use super::ToShape;
 impl ToShape for fj::Sweep {
     fn to_shape(&self, tolerance: Scalar, debug_info: &mut DebugInfo) -> Shape {
         sweep_shape(
-            self.shape.to_shape(tolerance, debug_info),
-            Vector::from([0., 0., self.length]),
+            self.shape().to_shape(tolerance, debug_info),
+            Vector::from([0., 0., self.length()]),
             tolerance,
         )
     }
 
     fn bounding_volume(&self) -> Aabb<3> {
-        let mut aabb = self.shape.bounding_volume();
-        aabb.max.z = self.length.into();
+        let mut aabb = self.shape().bounding_volume();
+        aabb.max.z = self.length().into();
         aabb
     }
 }