diff --git a/crates/engine/src/select.rs b/crates/engine/src/select.rs
index 550dd163c..421265ae1 100644
--- a/crates/engine/src/select.rs
+++ b/crates/engine/src/select.rs
@@ -193,8 +193,21 @@ pub(crate) fn in_window(d: &Drawing, e: &Entity, known: Option<Bounds2>, bx: &Bo
             pl.windows(2).any(|w| w.first().zip(w.get(1)).is_some_and(|(a, b)| seg_hits_box(*a, *b, bx)))
         }
     });
-    // A crossing box entirely inside a filled/text object also selects it.
-    hit || (eb.contains_box(bx) && matches!(e.kind, EntityKind::Text(_) | EntityKind::MText(_) | EntityKind::Insert(_)))
+    // A crossing box entirely inside a text/block bounding rectangle also selects it.
+    if hit || (eb.contains_box(bx) && matches!(e.kind, EntityKind::Text(_) | EntityKind::MText(_) | EntityKind::Insert(_))) {
+        return true;
+    }
+    // SOLID/TRACE are filled polygons. A crossing window wholly within the
+    // fill must select them even when it does not touch their outline. Check
+    // the polygon, not just its bounding rectangle (which can cover empty
+    // space around triangular solids).
+    if matches!(e.kind, EntityKind::Solid(_) | EntityKind::Trace(_)) && eb.contains_box(bx) {
+        return e.kind.prims().iter().any(|prim| match prim {
+            Prim::Fill(poly) => bx.corners().iter().all(|p| cadcraft_geom::point_in_polygon(poly, *p)),
+            _ => false,
+        });
+    }
+    false
 }
 
 /// Fence selection: entities crossed by the fence polyline.
@@ -255,3 +268,41 @@ mod tests {
         assert_eq!(fence_hits(EntityKind::Ray(line), [(5.0, 1.0), (5.0, 5.0)]), 0);
     }
 }
+
+#[cfg(test)]
+mod solid_interior_tests {
+    use super::*;
+
+    fn face(kind: bool, triangular: bool) -> Entity {
+        let a = Vec2::new(0.0, 0.0).to3(0.0);
+        let b = Vec2::new(10.0, 0.0).to3(0.0);
+        let c = Vec2::new(0.0, 10.0).to3(0.0);
+        let d = if triangular { c } else { Vec2::new(10.0, 10.0).to3(0.0) };
+        let solid = cadcraft_doc::Solid { corners: [a, b, c, d] };
+        Entity::new(Handle(256), if kind { EntityKind::Solid(solid) } else { EntityKind::Trace(solid) })
+    }
+
+    #[test]
+    fn crossing_window_inside_solid_and_trace_selects_fill() {
+        let inside = Bounds2::new(Vec2::new(4.0, 4.0), Vec2::new(6.0, 6.0));
+        for solid in [true, false] {
+            let mut d = Drawing::default();
+            let e = face(solid, false);
+            assert!(in_window(&d, &e, None, &inside, true, 0.01));
+            assert!(!in_window(&d, &e, None, &inside, false, 0.01));
+            d.model.push(e);
+            assert_eq!(select_window(&d, &Space::Model, inside, true), vec![Handle(256)]);
+            assert!(select_window(&d, &Space::Model, inside, false).is_empty());
+        }
+    }
+
+    #[test]
+    fn crossing_window_in_triangular_bbox_but_outside_fill_does_not_select() {
+        let d = Drawing::default();
+        let e = face(true, true);
+        let empty = Bounds2::new(Vec2::new(7.0, 7.0), Vec2::new(8.0, 8.0));
+        assert!(!in_window(&d, &e, None, &empty, true, 0.01));
+        let inside = Bounds2::new(Vec2::new(3.0, 3.0), Vec2::new(4.0, 4.0));
+        assert!(in_window(&d, &e, None, &inside, true, 0.01));
+    }
+}