diff --git a/common.scad b/common.scad
index db4f3bb..570ff8e 100644
--- a/common.scad
+++ b/common.scad
@@ -353,6 +353,7 @@ function segs(r) =
 // Arguments:
 //   $children = number of children the module has.  
 module no_children(count) {
+  assert($children==0, "Module no_children() does not support child modules");
   assert(count==0, str("Module ",parent_module(1),"() does not support child modules"));
 }
 
@@ -377,6 +378,7 @@ function _valstr(x) =
 //   expected = The value that was expected.
 //   info = Extra info to print out to make the error clearer.
 module assert_approx(got, expected, info) {
+    no_children($children);
     if (!approx(got, expected)) {
         echo();
         echo(str("EXPECT: ", _valstr(expected)));
@@ -404,6 +406,7 @@ module assert_approx(got, expected, info) {
 //   expected = The value that was expected.
 //   info = Extra info to print out to make the error clearer.
 module assert_equal(got, expected, info) {
+    no_children($children);
     if (got != expected || (is_nan(got) && is_nan(expected))) {
         echo();
         echo(str("EXPECT: ", _valstr(expected)));
diff --git a/strings.scad b/strings.scad
index cc0713b..5e34fd9 100644
--- a/strings.scad
+++ b/strings.scad
@@ -701,7 +701,9 @@ function str_format(fmt, vals, use_nbsp=false) =
 //   echofmt("{:-10s}{:.3f}", ["plecostamus",27.43982]);  // ECHO: "plecostamus27.440"
 //   echofmt("{:-10.9s}{:.3f}", ["plecostamus",27.43982]);  // ECHO: "plecostam 27.440"
 function echofmt(fmt, vals, use_nbsp=false) = echo(str_format(fmt,vals,use_nbsp));
-module echofmt(fmt, vals, use_nbsp=false) echo(str_format(fmt,vals,use_nbsp));
-
+module echofmt(fmt, vals, use_nbsp=false) {
+   no_children($children);
+   echo(str_format(fmt,vals,use_nbsp));
+}
 
 // vim: expandtab tabstop=4 shiftwidth=4 softtabstop=4 nowrap
diff --git a/structs.scad b/structs.scad
index e7effb4..1e9f321 100644
--- a/structs.scad
+++ b/structs.scad
@@ -101,6 +101,7 @@ function struct_echo(struct,name="") =
     undef;
 
 module struct_echo(struct,name="") {
+    no_children($children);
     dummy = struct_echo(struct,name);
 }
 
diff --git a/version.scad b/version.scad
index d10b338..b37d43f 100644
--- a/version.scad
+++ b/version.scad
@@ -49,6 +49,7 @@ function bosl_version_str() = version_to_str(BOSL_VERSION);
 // Description:
 //   Given a version as a list, number, or string, asserts that the currently installed BOSL library is at least the given version.
 module bosl_required(target) {
+    no_children($children);
     assert(
         version_cmp(bosl_version(), target) >= 0,
         str(
diff --git a/vnf.scad b/vnf.scad
index 05fd82f..edf00e4 100644
--- a/vnf.scad
+++ b/vnf.scad
@@ -341,9 +341,16 @@ function vnf_vertex_array(
 // Arguments:
 //   vnf = A VNF structure, or list of VNF structures.
 //   convexity = Max number of times a line could intersect a wall of the shape.
-module vnf_polyhedron(vnf, convexity=2) {
+module vnf_polyhedron(vnf,
+                      convexity=10,anchor="origin",cp,
+                      spin=0, orient=UP, extent=false
+)
+{
     vnf = is_vnf_list(vnf)? vnf_merge(vnf) : vnf;
-    polyhedron(vnf[0], vnf[1], convexity=convexity);
+    attachable(anchor=anchor, spin=spin, orient=orient, vnf=vnf, extent=extent, cp=is_def(cp) ? cp : vnf_centroid(vnf)){
+      polyhedron(vnf[0], vnf[1], convexity=convexity);
+      children();
+    }
 }