diff --git a/DOS33.pm b/DOS33.pm
index 065a3f0..9f1ab20 100644
--- a/DOS33.pm
+++ b/DOS33.pm
@@ -412,7 +412,9 @@ sub get_tslist {
   my ($dskfile, $tslist_trk, $tslist_sec) = @_;
 
   my ($next_tslist_trk, $next_tslist_sec) = ($tslist_trk, $tslist_sec);
+
   my @secs = ();
+
   do {
     ($next_tslist_trk, $next_tslist_sec, @secs) = get_tslist_sec($dskfile, $next_tslist_trk, $next_tslist_sec);
     if (defined $next_tslist_trk && $next_tslist_trk ne '') {
@@ -459,9 +461,7 @@ sub read_file {
   $mode = '' unless defined $mode;
   $conv = 0 unless defined $conv;
 
-  if (defined $dbg && $dbg) {
-    $debug = 1;
-  }
+  $debug = 1 if (defined $dbg && $dbg);
 
   my ($trk, $sec) = find_file($dskfile, $filename);
   if ($trk) {
@@ -490,5 +490,25 @@ sub read_file {
   }
 }
 
+sub unlock_file {
+  my ($dskfile, $filename, $dbg) = @_;
+
+  $debug = 1 if (defined $dbg && $dbg);
+
+  ##FIXME -- need to make find_file return catalog t/s & file offset.
+}
+
+sub lock_file {
+  my ($dskfile, $filename, $dbg) = @_;
+
+  $debug = 1 if (defined $dbg && $dbg);
+}
+
+sub delete_file {
+  my ($dskfile, $filename, $dbg) = @_;
+
+  $debug = 1 if (defined $dbg && $dbg);
+}
+
 1;
 
diff --git a/README b/README
index 0308c1d..f42f3ee 100644
--- a/README
+++ b/README
@@ -4,10 +4,10 @@ catalog.pl -- mostly working
 freemap.pl -- mostly working
 dos33read.pl -- mostly working for simple text files
 dos33write.pl
-dos33umlock.pl
-dos33lock.pl
+dos33umlock.pl -- started
+dos33lock.pl -- started
 dos33rename.pl
-dos33delete.pl
+dos33delete.pl -- started
 dos33copy.pl
 zap.pl -- partially working
 prozap.pl -- partially working
diff --git a/dos33delete.pl b/dos33delete.pl
new file mode 100644
index 0000000..60a3e3c
--- /dev/null
+++ b/dos33delete.pl
@@ -0,0 +1,29 @@
+#!/usr/bin/perl -w
+
+#
+# dos33delete.pl:
+#
+# Utility to delete a file on an Apple II DOS 3.3 disk image.
+#
+# 20190116 LSH
+#
+
+use strict;
+
+use DOS33;
+
+while (defined $ARGV[0] && $ARGV[0] =~ /^-/) {
+  # Debug
+  if ($ARGV[0] eq '-d') {
+    $debug = 1;
+    shift;
+  }
+}
+
+my $dskfile = shift or die "Must supply filename\n";
+my $filename = shift or die "Must supply filename\n";
+
+delete_file($dskfile, $filename, $debug);
+
+1;
+
diff --git a/dos33lock.pl b/dos33lock.pl
new file mode 100644
index 0000000..385677c
--- /dev/null
+++ b/dos33lock.pl
@@ -0,0 +1,29 @@
+#!/usr/bin/perl -w
+
+#
+# dos33lock.pl:
+#
+# Utility to lock a file on an Apple II DOS 3.3 disk image.
+#
+# 20190116 LSH
+#
+
+use strict;
+
+use DOS33;
+
+while (defined $ARGV[0] && $ARGV[0] =~ /^-/) {
+  # Debug
+  if ($ARGV[0] eq '-d') {
+    $debug = 1;
+    shift;
+  }
+}
+
+my $dskfile = shift or die "Must supply filename\n";
+my $filename = shift or die "Must supply filename\n";
+
+lock_file($dskfile, $filename, $debug);
+
+1;
+
diff --git a/dos33unlock.pl b/dos33unlock.pl
new file mode 100644
index 0000000..8121818
--- /dev/null
+++ b/dos33unlock.pl
@@ -0,0 +1,29 @@
+#!/usr/bin/perl -w
+
+#
+# dos33unlock.pl:
+#
+# Utility to unlock a file on an Apple II DOS 3.3 disk image.
+#
+# 20190116 LSH
+#
+
+use strict;
+
+use DOS33;
+
+while (defined $ARGV[0] && $ARGV[0] =~ /^-/) {
+  # Debug
+  if ($ARGV[0] eq '-d') {
+    $debug = 1;
+    shift;
+  }
+}
+
+my $dskfile = shift or die "Must supply filename\n";
+my $filename = shift or die "Must supply filename\n";
+
+unlock_file($dskfile, $filename, $debug);
+
+1;
+