Welcome. I'm not sure which book or online course you are talking about. Maybe a link would be helpful.
In the meantime there is a thread here on QB that may be of interest to you.
Review of Westalee Rulers Course There are some older
Related Topics regarding Westalee rulers. You could also do a search here that may give some more recent posts. (I do a search for
Posts, rather than
Topics as there are some threads that are many pages long and may only be mentioned once.)
Here are a couple of other links I found in my search:
https://user-13729161406.cld.bz/Quil...ewing-Machine1
https://www.sewsteady.com/wp-content...OAD_060618.pdf
YWIA