I am new to moulds. I worked through Gary Priester's October 2001 on the flag and was encouraged. Then I found Tony Roberts suite of moulds and his 2002 Guest Tutorial (#12) Mould Mania. As I followed his instructions (I think) I ended up with an error message which I can't seem to avoid. I obviously misunderstand something. Here's what I did:

1 Created a 300 x 200 rectangle.
2 Applied a default mould to it.
3 With shape editor clicked on top left corner, clicked on top handle on left side and moved it (gathered it?) up to top left corner. Repeated step with other bottom left side handle and gathered it to bottom left corner.
4 Repeated step 3 with right side.
5 Still with shape editor clicked on top left corner, clicked on left handle on top side and dragged it down 150. Clicked on right handle on top side and dragged it up 150.
6 Repeated step 5 with bottom.
7 Moved mould (status line calls it a mould) out of the way.
8 Created banner 400 x 50.
9 Moved mould over banner and sized to fit over banner.
10 Cut mould. Selected banner. Selected mould tool. Selected paste envelope.
11 Received error message - "This shape is not suitable for use as an envelope mould. Envelope moulds must have four sides."

What am I doing wrong?

Thanks in advance for your help.

Les