trestle assemble is not generating files where expected.
**Describe the bug**
Trestle assemble is meant to inject content into dist/OSCAL_MODEL_PLURAL/object_name.{json, yml}

At this point it is not.

**To Reproduce**
trestle init
trestle create catalog -n my-catalog
trestel assemble catalog -n my-catalog
ls dist/catalogs/
(No file)

**Expected behavior**
trestle init
trestle create catalog -n my-catalog
trestel assemble catalog -n my-catalog
ls dist/catalogs/
my-catalog.json



diff --git a/tests/trestle/core/commands/assemble_test.py b/tests/trestle/core/commands/assemble_test.py
index 65c54707..a77417ce 100644
--- a/tests/trestle/core/commands/assemble_test.py
+++ b/tests/trestle/core/commands/assemble_test.py
@@ -65,7 +65,7 @@ def test_assemble_catalog(testdata_dir: pathlib.Path, tmp_trestle_dir: pathlib.P
         assert rc == 0
 
     # Read assembled model
-    actual_model = Catalog.oscal_read(pathlib.Path('dist/catalog.json'))
+    actual_model = Catalog.oscal_read(pathlib.Path('dist/catalogs/mycatalog.json'))
     _, _, expected_model = load_distributed(mycatalog_dir / 'catalog.json')
 
     assert actual_model == expected_model
diff --git a/trestle/core/commands/assemble.py b/trestle/core/commands/assemble.py
index 04fbdbd8..d7c9f32e 100644
--- a/trestle/core/commands/assemble.py
+++ b/trestle/core/commands/assemble.py
@@ -181,7 +181,10 @@ class AssembleCmd(Command):
 
         # distributed load
         _, _, assembled_model = load_distributed(root_model_filepath)
-        assembled_model_filepath = trestle_root / const.TRESTLE_DIST_DIR / f'{model_alias}.{args.extension}'
+        plural_alias = model_alias if model_alias[-1] == 's' else model_alias + 's'
+        assembled_model_dir = trestle_root / const.TRESTLE_DIST_DIR / plural_alias
+
+        assembled_model_filepath = assembled_model_dir / f'{args.name}.{args.extension}'
 
         plan = Plan()
         plan.add_action(CreatePathAction(assembled_model_filepath, True))
['trestle/core/commands/assemble.py', 'tests/trestle/core/commands/assemble_test.py']