diff --git a/builders.py b/builders.py
index 5317811..d5ca36b 100644
--- a/builders.py
+++ b/builders.py
@@ -85,7 +85,7 @@ new_output_folder.cleaner = lambda: shutil.rmtree(build_state['public_wiki_folde
 @tzk_builder
 def export_public_tiddlers(export_filter: str) -> None:
     "Export public tiddlers to public wiki folder"
-    assert 'public_wiki_folder' in build_state
+    assert 'public_wiki_folder' in build_state, "new_output_folder builder must run first"
     tw.exec((
         ("savewikifolder", build_state['public_wiki_folder'], export_filter),
     ))
@@ -106,8 +106,9 @@ def _find_kill_phrases(phrases: Set[str]):
     return failures
 
 @tzk_builder
-def check_for_kill_phrases(kill_phrase_file: str = None):
+def check_for_kill_phrases(kill_phrase_file: str = None) -> None:
     "Fail build if any of a series of regexes appears in a tiddler's source"
+    assert 'public_wiki_folder' in build_state, "new_output_folder builder must run first"
     if kill_phrase_file is None:
         kill_phrase_file = "tiddlers/_system/config/zettelkasten/Build/KillPhrases.tid"
 
@@ -128,3 +129,16 @@ def check_for_kill_phrases(kill_phrase_file: str = None):
             result.append(f"'{failed_regex.pattern}' matched file {trimmed_file}:\n"
                           f"    {failed_line.strip()}")
         stop('\n'.join(result))
+
+@tzk_builder
+def save_attachments_externally(attachment_filter: str = "[is[image]]",
+                                extimage_folder: str = "images") -> None:
+    "Save embedded files in the wiki into an external folder"
+    assert 'public_wiki_folder' in build_state
+    tw.exec(
+        (
+            ("savetiddlers", attachment_filter, extimage_folder),
+        ),
+        base_wiki_folder=build_state['public_wiki_folder']
+    )
+
diff --git a/tw.py b/tw.py
index 2c5ab05..06fca49 100644
--- a/tw.py
+++ b/tw.py
@@ -39,8 +39,10 @@ def _whoami() -> str:
         return "user"
 
 
-def exec(args: Sequence[Sequence[str]]) -> int:
+def exec(args: Sequence[Sequence[str]], base_wiki_folder: str = None) -> int:
     call_args = [_tw_path()]
+    if base_wiki_folder is not None:
+        call_args.append(base_wiki_folder)
     for tw_arg in args:
         call_args.append(f"--{tw_arg[0]}")
         for inner_arg in tw_arg[1:]:
diff --git a/tzk.py b/tzk.py
index c232367..453fa17 100644
--- a/tzk.py
+++ b/tzk.py
@@ -197,6 +197,7 @@ class BuildCommand(CliCommand):
                 traceback.print_exc()
                 sys.exit(1)
 
+        # TODO: This should run in a finally() block; leaving for now as it's convenient for development :)
         for idx, step in enumerate(steps, 1):
             if hasattr(step, 'cleaner'):
                 print(f"\ntzk: Running cleanup routine for step {idx}...")