diff --git a/crates/mesh/src/quality/mod.rs b/crates/mesh/src/quality/mod.rs
index 8f7b527..d86c49c 100644
--- a/crates/mesh/src/quality/mod.rs
+++ b/crates/mesh/src/quality/mod.rs
@@ -35,7 +35,8 @@ use fieldcraft_model::{ElementKind, admissible_jacobian, check_coordinates, tet4
 pub use conformity::{Conformity, conformity};
 pub use jacobian::{JacobianCheck, Validity};
 pub use report::{
-    GateOptions, GateReport, MetricStats, QualityReport, enclosed_volume, quality_report, validity_gate, validity_gate_checks, validity_gate_elements,
+    GateOptions, GateReport, Marked, MetricStats, QualityReport, enclosed_volume, mark_elements, quality_report, validity_gate, validity_gate_checks,
+    validity_gate_elements,
 };
 pub(crate) use shape::{planar_corner, quad_axes};
 
@@ -77,6 +78,26 @@ pub enum Metric {
 }
 
 impl Metric {
+    pub const ALL: [Metric; 12] = [
+        Metric::ScaledJacobian,
+        Metric::JacobianRatio,
+        Metric::Shape,
+        Metric::MinDihedral,
+        Metric::MaxDihedral,
+        Metric::RadiusRatio,
+        Metric::AspectRatio,
+        Metric::VolumeLength,
+        Metric::EdgeRatio,
+        Metric::MinAngle,
+        Metric::MaxAngle,
+        Metric::Skew,
+    ];
+
+    /// The metric named `name` ([`Metric::name`]).
+    pub fn parse(name: &str) -> Option<Metric> {
+        Metric::ALL.into_iter().find(|m| m.name() == name)
+    }
+
     pub fn name(self) -> &'static str {
         match self {
             Metric::ScaledJacobian => "scaled_jacobian",
diff --git a/crates/mesh/src/quality/report.rs b/crates/mesh/src/quality/report.rs
index 1800843..095964f 100644
--- a/crates/mesh/src/quality/report.rs
+++ b/crates/mesh/src/quality/report.rs
@@ -144,6 +144,71 @@ pub fn quality_report(model: &Model, labels: Option<&[u32]>, bins: usize) -> Res
     Ok(report)
 }
 
+/// An element that fails a quality limit, or is not proven valid.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Marked {
+    pub label: u32,
+    pub kind: ElementKind,
+    /// The mean of its nodes.
+    pub centroid: [f64; 3],
+    /// The certified validity, for solids.
+    pub validity: Option<Validity>,
+    /// Each limit it fails: the metric, its value and the limit.
+    pub failed: Vec<(Metric, f64, f64)>,
+    /// Its scaled Jacobian, when it has one (the worst-first order).
+    pub scaled_jacobian: Option<f64>,
+}
+
+impl Marked {
+    /// Not proven valid (inverted or undetermined).
+    pub fn is_invalid(&self) -> bool {
+        matches!(self.validity, Some(Validity::Invalid | Validity::Undetermined))
+    }
+}
+
+/// The elements (all, or the given labels) that fail a limit: a value below the limit of a
+/// metric where higher is better ([`Metric::higher_is_better`]), above it otherwise, or no value
+/// (NaN). Solids not proven valid are always marked. A metric an element does not have does not
+/// apply to it. Returns how many elements were measured and the marked ones, worst first: not
+/// valid, then by scaled Jacobian (lowest first; none counts as 1), then by label.
+pub fn mark_elements(model: &Model, labels: Option<&[u32]>, limits: &[(Metric, f64)]) -> Result<(usize, Vec<Marked>)> {
+    if let Some((m, v)) = limits.iter().find(|(_, v)| !v.is_finite()) {
+        return Err(Error::Invalid(format!("the limit of {} must be a finite number, got {v}", m.name())));
+    }
+    let mut measured = 0;
+    let mut marked = Vec::new();
+    for (label, element) in selection(model, labels)? {
+        if !is_measured(element.kind) {
+            continue;
+        }
+        let xyz = coordinates(model, label, element)?;
+        let q = element_quality(element.kind, &xyz)?;
+        measured += 1;
+        let failed: Vec<(Metric, f64, f64)> = limits
+            .iter()
+            .filter_map(|&(metric, limit)| {
+                let v = q.get(metric)?;
+                let fails = v.is_nan() || if metric.higher_is_better() { v < limit } else { v > limit };
+                fails.then_some((metric, v, limit))
+            })
+            .collect();
+        let validity = q.validity();
+        let invalid = matches!(validity, Some(Validity::Invalid | Validity::Undetermined));
+        if failed.is_empty() && !invalid {
+            continue;
+        }
+        let n = xyz.len().max(1) as f64;
+        let centroid = [0, 1, 2].map(|k| xyz.iter().map(|p| p[k]).sum::<f64>() / n);
+        marked.push(Marked { label, kind: element.kind, centroid, validity, failed, scaled_jacobian: q.get(Metric::ScaledJacobian) });
+    }
+    let key = |m: &Marked| (!m.is_invalid(), m.scaled_jacobian.filter(|v| !v.is_nan()).unwrap_or(1.0));
+    marked.sort_by(|a, b| {
+        let (ka, kb) = (key(a), key(b));
+        ka.0.cmp(&kb.0).then(ka.1.total_cmp(&kb.1)).then(a.label.cmp(&b.label))
+    });
+    Ok((measured, marked))
+}
+
 /// What the validity gate checks besides element validity.
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct GateOptions {
diff --git a/crates/mesh/src/quality/tests.rs b/crates/mesh/src/quality/tests.rs
index dee4977..0bd50b8 100644
--- a/crates/mesh/src/quality/tests.rs
+++ b/crates/mesh/src/quality/tests.rs
@@ -309,3 +309,29 @@ fn report_and_gate() {
     assert!(validity_gate(&model, &GateOptions { expected_volume: Some(f64::NAN), ..Default::default() }).is_err());
     assert!(enclosed_volume(&c, &[[0, 1, 99]]).is_err());
 }
+
+/// A cube passes; a sheared hex fails a scaled-Jacobian floor above its value and passes one
+/// below; a mirrored hex is marked whatever the limits; worst first.
+#[test]
+fn marks_elements_below_their_limits() {
+    let sheared: Vec<[f64; 3]> = UNIT_CUBE.iter().map(|c| [c[0] + 0.75 * c[2], c[1], c[2]]).collect();
+    let mirrored: Vec<[f64; 3]> = UNIT_CUBE.iter().map(|c| [-c[0], c[1], c[2]]).collect();
+    let m = model_of(&[(ElementKind::Hex8, UNIT_CUBE.to_vec()), (ElementKind::Hex8, sheared), (ElementKind::Hex8, mirrored)]);
+    let (measured, marked) = mark_elements(&m, None, &[(Metric::ScaledJacobian, 0.9)]).unwrap();
+    assert_eq!(measured, 3);
+    assert_eq!(marked.iter().map(|k| k.label).collect::<Vec<_>>(), [3, 2]);
+    assert!(marked[0].is_invalid());
+    let (f, v, limit) = marked[1].failed[0];
+    assert_eq!((f, limit), (Metric::ScaledJacobian, 0.9));
+    assert!(close(v, 0.8));
+    assert!(close(marked[1].centroid[0], 0.5 + 0.375) && close(marked[1].centroid[2], 0.5));
+    let (_, loose) = mark_elements(&m, None, &[(Metric::ScaledJacobian, 0.5), (Metric::EdgeRatio, 10.0)]).unwrap();
+    assert_eq!(loose.iter().map(|k| k.label).collect::<Vec<_>>(), [3]);
+    // An edge ratio ceiling below the sheared hex's (its slanted edges are 1.25 long).
+    let (_, edges) = mark_elements(&m, Some(&[2]), &[(Metric::EdgeRatio, 1.2)]).unwrap();
+    assert_eq!(edges.len(), 1);
+    assert!(mark_elements(&m, None, &[(Metric::ScaledJacobian, f64::NAN)]).is_err());
+    assert!(mark_elements(&m, Some(&[9]), &[]).is_err());
+    assert_eq!(Metric::parse("min_dihedral"), Some(Metric::MinDihedral));
+    assert!(Metric::ALL.iter().all(|m| Metric::parse(m.name()) == Some(*m)));
+}