--- /dev/null
+polyline p 0 0 0 5 0 0 5 0 3 3 0 3 3 0 5 0 0 5 0 0 0
+mkplane f p
+prism s f 0 5 0
+explode s f
+donly s
+offsetparameter 1e-7 c i
+offsetload s 1
+offsetonface s_4 5
+offsetperform result
+
+checkprops result -v 441
+
+checknbshapes result -shell 1