diff --git a/crates/engine/src/cmd/hatch.rs b/crates/engine/src/cmd/hatch.rs
index 308c7d7d..5a77e934 100644
--- a/crates/engine/src/cmd/hatch.rs
+++ b/crates/engine/src/cmd/hatch.rs
@@ -21,7 +21,7 @@ pub use pick::{HatchPicks, PickMode};
 
 pub fn specs() -> Vec<CommandSpec> {
     vec![
-        CommandSpec::new("hatch", "Hatch...", run_hatch).menu(&["Draw", "Hatch..."]).alias(&["h", "bh", "-hatch"]).params("{points?: [[x,y]] (internal points) and/or handles?: [hex] (closed objects), pattern?: \"ANSI31\", scale?, angle? (degrees), associative? (HPASSOC), separate? (HPSEPARATE: a hatch per point/object), origin?: [x,y] (HPORIGIN) | originMode?: \"current\"|\"bottomLeft\"|\"bottomRight\"|\"topLeft\"|\"topRight\"|\"center\" (HPORIGINMODE), style?: \"normal\"|\"outer\"|\"ignore\" (HPISLANDDETECTION)} — gaps up to HPGAPTOL close").interactive(|s| Ok(Box::new(HatchM::new(s, false)))),
+        CommandSpec::new("hatch", "Hatch...", run_hatch).menu(&["Draw", "Hatch..."]).alias(&["h", "bh", "-hatch"]).params("{points?: [[x,y]] (internal points) and/or handles?: [hex] (closed objects), pattern?: \"ANSI31\" (built in, or defined by patternFile | patternText), patternFile?: path to a .pat file | patternText?: its contents (loads the patterns it defines), scale?, angle? (degrees), associative? (HPASSOC), separate? (HPSEPARATE: a hatch per point/object), origin?: [x,y] (HPORIGIN) | originMode?: \"current\"|\"bottomLeft\"|\"bottomRight\"|\"topLeft\"|\"topRight\"|\"center\" (HPORIGINMODE), style?: \"normal\"|\"outer\"|\"ignore\" (HPISLANDDETECTION)} — gaps up to HPGAPTOL close").interactive(|s| Ok(Box::new(HatchM::new(s, false)))),
         CommandSpec::new("gradient", "Gradient...", run_gradient).menu(&["Draw", "Gradient..."]).alias(&["gd"]).params("{points? and/or handles?, name?: \"LINEAR\"|\"CYLINDER\"|\"CURVED\"|\"SPHERICAL\"|\"HEMISPHERICAL\" or INV… (colours swapped), color1?, color2?, angle? (degrees), centered? (default true)}").interactive(|s| Ok(Box::new(HatchM::new(s, true)))),
         CommandSpec::new("boundary", "Boundary...", run_boundary).menu(&["Draw", "Boundary..."]).alias(&["bo", "bpoly"]).params("{points: [[x,y]]}").interactive(|_| Ok(Box::new(BoundaryM { region: false }))),
         CommandSpec::new("region", "Region", run_region).menu(&["Draw", "Region"]).alias(&["reg"]).params("{handles?}"),
@@ -458,7 +458,7 @@ fn run_hatch(s: &mut Session, p: &Value) -> Result<Value> {
         && cadcraft_doc::library::pattern(&up).is_none()
         && patfile::user_pattern(&up).is_none()
     {
-        return Err(bad("hatch", format!("unknown pattern {up}")));
+        return Err(bad("hatch", format!("unknown pattern {up}: not built in; load it with patternFile or patternText (a .pat file)")));
     }
     make(s, p, false)
 }
@@ -840,6 +840,16 @@ mod tests {
         assert!(s.current_prompt().unwrap().picker.is_none());
     }
 
+    #[test]
+    fn unknown_pattern_error_and_catalog_name_the_pat_file_route() {
+        let mut s = Session::new();
+        s.execute("rectang", &json!({ "p1": [0, 0], "p2": [10, 10] })).unwrap();
+        let e = s.execute("hatch", &json!({ "points": [[5, 5]], "pattern": "GRAVEL" })).unwrap_err();
+        assert!(e.to_string().contains("patternFile"), "{e}");
+        let spec = specs().into_iter().find(|c| c.id == "hatch").unwrap();
+        assert!(spec.params.contains("patternFile") && spec.params.contains("patternText"), "{}", spec.params);
+    }
+
     #[test]
     fn json_hatch_refuses_an_undefined_pattern() {
         let mut s = Session::new();